# Diy lightwieght concrete background (56k beware)



## iceblue

Beginings.









Completed sections out of tank.









Protective foam.









Starting a stack.









Getting taller.









Stack almost complete.









Before skin coat.









Section with skin coat.









Comments and questions welcome.


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## Stickzula

What concrete did you use? did you add fortifier or something to make the mix stronger/more rigid?


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## iceblue

The rough structure is a mixture of type II cement, some sand and a lot of perlite. I experimented with a lot of different mixtures and came up with a with a formula that is just heavier than water but more lightwieght than regular concrete. I didn't use any fortifiers but did use more cement than would normally be found in regular concrete. Sometimes refered to as a "Hot mix". For the pipework I also added a couple of cups of shreaded fiberglass to help prevent cracking around the pvc.


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## becikeja

Did you use any color dyes in the mix, or is that natural?


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## iceblue

The last picture has concrete dye painted over the skin coat. Heres what a completed section looks like without the color added.










Some of the pictures were taken without flash using a low wattage bulb for illumination. They show a little more detail but it does skew what the actual color is.

I'm going to have to do somemore experimenting with the liquid concrete dye. I painted it directly to the dried skin coat but it does not stick very well. You can rub it off with your fingers.  I'm going to try mixing the dye with powdered cement and water to see if this will help with drying the color onto the structures.


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## Number6

iceblue said:


> The rough structure is a mixture of type II cement, some sand and a lot of perlite.


 This is very interesting! Any chance you could write up that recipe?


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## iceblue

I've adjusted the mixture a bit while building the structures but am happy with this formula.
9 cups portland typeII cement
3 cups plaster sand
12 cups of water
24 cups of perlite

Dry mix the sand and cement together and add 10 cups of water holding 2 cups in reserve. Stir well.
To this slurry add 24 generous cups of Perlite and mix gently. I use a 1" pvc pipe for this part. It works well and is pretty easy on the perlite. Stir while at the same time pulling up the slurry from the bottom of the bucket. Mix untill the perlite is well covered adding a little water from the reserve to help in the mixing. Careful as you add the reserved water at this point. You want a high slump that will hold its shape to build your structures. To much water and you won't be able to work with it.

For the skin coat I use a mixture of 1 part Type II cement to 3 parts plaster sand. Be carefull here also with the water. Add it a little at a time and mix well. You wan't a mix thats not to dry as it won't stick or to wet as it will sluff off. When I skin the rest of my structure I'm going to add concrete glue to the mix to help with stickiness.

I might also add that as I build these structure in tank a layer at a time. I use a cold moisture humidifier to keep the humidity up. Once I start a structure thier kept in high humidity untill thier done. Usually 3-4 days. I use a bedding sheet to cover the front of the aquarium to keep the moisture in.


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## iceblue

The mix I described will do this much. The three dark structures plus one of equal size in the other back corner of the tank.










The beer bottle will give you a good idea of the size of this project. This is one of only a few diy projects I would recommend the drinking of libations because there are no power tools involved.


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## Number6

awesome, thanks... nice photo! I'll use it as proof that the recipe called for beer! 
I just wont say where the beer is poured :lol:


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## iceblue

Thought I would show what my design is based on. It actually is a Lake Malawi biotope. I had thought about making the usual jumbled rock background but was having problems designing the number of caves into it that I wanted and still have a natural look. Mara point solved many of these issues.

The stuctures are based on the center right photo.
http://home.cogeco.ca/~ductapediver/Lar ... %20pg4.htm

Larry Johnson (aka Larryochromis) was kind enough to give me a few tips on the formations and give me a link to another diy background thats going to help later on in the project. :thumb: Thanks again Larry.


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## bibbs68

hello iceblue, just wanting to check in and see how your project is going. Looking good so far!


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## Rivermud

Looks like Sulfer Vents in those pictures.. I'd be curious to see if they were.


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## iceblue

Hey bibbs68.
I haven't been able to get as far as I wanted when i started these new sections. We're short handed at work and I've been putting in 12 - 14 hrs a day and weekends. Not a whole lot of energy left at the end of the day to mix concrete by hand. :lol:

I have the 4 new sections almost built to the top and I'm hoping to finish the stacks and get them skinned this weekend.









I already have 30 caves with with 40 entrances of different sizes built into what I've completed so far. The areas in between the stacks won't have any so they should go a lot quicker.









Interesting thought on the Mara Point "Pagoda stones" formations Rivermud. I was thinking along the lines of vertically striated rock that had been weather worn and then submerged somewhere along the line.

Here's another picture of these formations that are a little different in look. Bottom left hand side. http://users.pandora.be/cichlidae/Themas/biotopen_1.htm


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## Turtlemaxxx

> Careful as you add the reserved water at this point. You want a high slump that will hold its shape to build your structures.


Just for clarification, did you mean you want LOW slump? Because high slump would mean its turning into a puddle. But thanks for the recipe, it will come in handy when i get around to formations in my 180.

-matt


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## iceblue

Turtlemaxxx said:


> Just for clarification, did you mean you want LOW slump? Because high slump would mean its turning into a puddle. But thanks for the recipe, it will come in handy when i get around to formations in my 180.
> 
> -matt


It's been a long time since I've poured any slabs. We use to have the truck pour a little out on the ground to see how it stacked. If it stacked too high we would have them add a little water so it was easier to work. Pouring concrete in the desert in the middle of summer is sooo much fun. 

Thanks for the clarification Matt. I would hate for somebody to mix a batch and then write back that my recipe sucked because of a terminology mistake. :lol:

The mix should be just wet enough to be sticky and hold its shape but not so dry that it will crumble apart when you try to form it. If its too wet and won't hold its shape you can add a little more cement and perlite to the mix untill you get something your comfortable with.


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## Exodus1500

I LOVE that you are going with a natural design. Often I like setting up a tank just as much as I enjoy the fish in it.... I am a huge fan of aqua scaping. Im sure it would be difficult, but if you could make a few of those stalagmite looking formations freestanding in the center, it would look amazing. actually, if you formed them with some sprayfoam and then used your cement technique it probably would go over easily enough.


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## iceblue

Actually, I'm useing a lightweight concrete mix to stay away from sprayfoams and styrofoam allthough I may use a sprayfoam to disquise my overflow boxes. It's much easier for me to design caves into these structures and I don't have to worry about anything floating on me or the styrofoam degrading over time.

If you look at the second to last photo I posted you can see the base of one of the structures I'm going to use to split the tank into thirds. My undergravel jet system will be circulating water counterclockwise in each of the three sections with the center structures seperating them. My return lines from the sump will be at each end of the tank one at the front and one at the back about halfway down and pointed towards the overflow boxes also located one to the front and one to the back opposite the returns. This arrangment will also keep the water moving counterclockwise. The center structures will be at different hieghts along this flow pattern and I'm hoping this will along with the jet system give me a kind vortex pattern that will aid in keeping detritus off the bottom of the tank and flowing towards my filter.


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## Exodus1500

Please, forgive my ignorance here, but don't you have to apply some sort of sealant over the cement, lest it will leak toxins?


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## iceblue

The biggest problem with concrete/mortar backgrounds is the leaching of minerals that raises your hardness to very high levels. I'm hoping to avoid this by having a very long curing time before adding water. Once I do add the water I will also be doing a very long fishless cycle. This should establish bacterias and algae on the structures and seal them further. I'm thinking I'll be feeding the tank ammonia for quite a while while I save up for the fish stock I want to get.

I know that back in the 70s when earth sheltered homes were becoming popular some of them had a problem with radon emminating from the concrete walls. But that had more to do with where the rock for the concrete had been mined than with the cement itself.


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## iceblue

Well... I finally got the back wall done. There is nothing fast when it comes to building these things but I'm real happy with the results I've gotten so far.

While waiting for the concrete to dry between steps I've been buttoning up a lot of things on the tank. When the background is done I'll no longer have any excuses not to get the glass and fill it up with water.

This is a pic looking down one side of the tank in ambient light.









This one is with my lighting system on. I'm real happy with these security lights. Thier 6500k with a CRI of 92. It's a very clean light slightly in the blue range. Thier are 2 of them and they use only 65watts each but give you the equivalancy 500 watts of lighting per bulb.









I know a lot of people are fat on LEDs these days but I just love the way my cold cathodes light up this tank. There are 6 of them and pictures just don't do justice to what they look like when your standing right in front of it.


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## Mcdaphnia

That last shot of the "Pagoda stones" looks even more like basalt.

http://www.spokaneoutdoors.com/basalt.htm

Some volcanic rock has a similar appearance.

http://www.lindahall.org/events_exhib/e ... n/50.shtml


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## iceblue

Mcdaphnia said:


> That last shot of the "Pagoda stones" looks even more like basalt.


Early on in this tank project I spent a lot of time looking for geological maps of the Lake Malawi area. At the time I wasn't really sure what direction or method I was going to use to build the background but I did find a very good map showing the type of rock that overlayed most of the area around the lake. By the time I did decide what I was going to do I no longer could find the link to the map. :x I tied a rope to my ankle and and threw it over my shoulder and began pulling on it for not saving it to favorites or something. It would have at least allowed me to make a pretty good guess as to what the formations were.

Malawi is a mixed bag of rock type and all in all I'm still happy with the direction my projects going even if it is a bit styleized. If only I knew what color/s they were.... :?


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## Mcdaphnia

iceblue said:


> .... If only I knew what color/s they were.... :?


 Green! That's what they mean by Aufwuchs.

http://www.cichlid-forum.com/articles/aufwuchs.php


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## iceblue

:lol: I'm hoping thats what I get eventually but I'm not sure if my lights will be strong enough to punch down to the bottom of the tank to maintain a healthy crop.


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## Mcdaphnia

iceblue said:


> :lol: I'm hoping thats what I get eventually but I'm not sure if my lights will be strong enough to punch down to the bottom of the tank to maintain a healthy crop.


 Basalts and similar volcanic rocks are often dark gray or brown. They may be reddish or yellowish due to other minerals. I threw lots of oak leaves in as my rocks naturalised. Some rocks turned dark brown while others or parts of the same rock stayed gray. I didn't expect it to be permanent, but almost a year later, I could still see the color differences. Hopefully your ammonia treatment will also encourage some green as well as beneficial bacteria, and oak leaves during the fishless cycle shouldn't hurt anything though they are slightly acidic (tannic acid). I had plenty fo algae growing right on the leaves.

P. S. Some cool geology maps of Lake Malawi here:

http://rock.geosociety.org/limno/files/ ... l_2006.pdf


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## iceblue

Mcdaphnia said:


> Hopefully your ammonia treatment will also encourage some green as well as beneficial bacteria, and oak leaves during the fishless cycle shouldn't hurt anything though they are slightly acidic (tannic acid). I had plenty fo algae growing right on the leaves.
> 
> P. S. Some cool geology maps of Lake Malawi here:
> 
> http://rock.geosociety.org/limno/files/ ... l_2006.pdf


You got me to looking around on the net again and now I have a headache. Trying to learn geology in a couple of afternoon sittings is near impossible. Closet I could figure out is that they could possibly be precambrian columnular igneous basalt. Minerals and organic growth also play a role in the actual surface color of the stone. I've decided to paint them to match some of the basalts from Wisconsin. Should make for nice looking formations. :thumb: http://images.search.yahoo.com/search/i ... 0&ei=UTF-8

Oak leaves are in short supply here in Vegas although I can get my hands on plenty of pine needles. I know thier on the high end of acidic but I'm worried about thier high resin content also. I may just have to stick with a long cure time before I add water and plenty of water changes after cycling the tank.


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## jcollette3

Looking good. Are you going for a columnar basalt look? Columnar joints form in slowly cooling flood basalts (where large volumes of basalt issue from cracks int he ground and cover vast regions from 10's to 1000's of m thick). As the basalt body cools, contraction occurs within the body, starting from both the bottom and top of the flow. This contraction is spread throughout the body, and since the lava is already partially solidified, it cant move about, so small scale cracks and planes of weakness form as a result. These things can be spectacularly geometric. Here are some images I found on a quick yahoo image search.



















The color is caused by oxidation of metals that are contianed in the basalt, primarily as Fe and Mg. The color is usually a nice deep red brown, but whack a piece open with a hammer sometime. The interior is a deep steel gray. If you have any other basalt or rock related questions send me a pm, I'm a geologist.


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## iceblue

Well... I have an update on progress. All the structures are done and I'm ready to paint/color. As I had stated earlier, thier is nothing quick about building backgrounds this way. If you don't have patiance I wouldn't recommend it.

Here are a few pics showing the structures that divide the tank.

Left of center.









Right of center.









A couple of randoms.


















These are the frames I built to hide the pumps that will be feeding my UGF. If I have a problem with the pump the whole structure will be easy enough to pull out and up to perform maintainance.









Here's one of them in place and being covered with the concrete mix. The grey tube is to hold the outlet for my return line from the sump in place and, in the direction I want the flow to go.









Front and back view of one of the false fronts after they were completed. Both of them stand up on thier own amazingly enough. The shelf at the top is for mechanical filter material, probably a course sponge.


















Side veiw.


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## nicholas316

not bad!


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## remarkosmoc

WOW. That is really nice, I've never had the skill or patience for sculpting. Good job. Please post pics of the finished project when it's done.


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## jcollette3

Looking good! What did your research into to the rock type of these structures turn up? I wish there was a _good_ geological map of the rift lakes area - now that would be a great resource.


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## iceblue

Thanks for the compliments. 



jcollette3 said:


> Looking good! What did your research into to the rock type of these structures turn up? I wish there was a _good_ geological map of the rift lakes area - now that would be a great resource.


After many frustrating hours of surfing I couldn't find anything difinetive. As you had pointed out Mara point is in an area of origeny and could possibly be of sedimentary/metamorphic make-up. Right now I'm leaning towards painting it to look like gniess useing this picture as a guide. http://www.foxislandalliance.org/brochu ... ock19c.jpg The colors may change but the application will be similar.

Another interesting pic I found is from Australia. The appearance is very much like the formations at Mara point. http://farm1.static.flickr.com/63/17357 ... 81.jpg?v=0 I'm still kind of undecided whether to paint the base of the formations to look like sedimentary rock with "pebbles" coming up out of it or just going with the gniess look.


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## Exodus1500

looking great. The first link "rock19c.jpg" looks like the same color as the granite in my 45g


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## jcollette3

That's some nice gneiss in the first pic! Ha - sorry, bad geology pun! That color scheme will look fantastic. What will you use for paint/pigment?


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## iceblue

I plan to use Sika top seal 107 that uses a polymer liquid for mixing. Colors can be added to it well. I've found a couple of places here in Sin City that carry it but none of them are opened on the weekends and I've been real busy putting in long days at work during the week. If the cost is too much I may just use regular cement and coloring with a little water added.

The first coat will cover all the structures in black. It's hard to see in the posted pics but all the formations have vertical striations worked into them with a small soft bristled wisk brush. As I add dots of different size and colors verticaly up and down the structures I'm expecting that the black within the surface scratches will give it a layered look much like metamorphic rock in which the crytaline strutures were rapidly cooled and not as fully formed as you would find in something like granite.


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## jcollette3

Can't wait to see it finished! You'll certainly have some happy fish.


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## theamazonian

Amazing!


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## AE0N

Im really looking forward to seeing this finished.

I love going down into underground caves and it reminds me of some of the rock formations you see in them.

Good work.


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## mcflyyy

Hi Iceblue,
Thanks for a great idea, although mine will be on a much smalley scale!



iceblue said:


> The biggest problem with concrete/mortar backgrounds is the leaching of minerals that raises your hardness to very high levels. I'm hoping to avoid this by having a very long curing time before adding water. Once I do add the water I will also be doing a very long fishless cycle....


I am on a bit of a timeframe though, as the poor fish I have stuck in a crowded tank need to get some space ASAP :fish:

Is there a sealer available, or a lighter mix (maybe a plaster) you could recommend to be safe fairly soon after drying?
Cheers,
Mcflyyy


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## iceblue

Plasters are pretty heavy as they get thicker. If you look at the stickys posted at the top of the DIY discussion forum you'll see one for backgrounds. Most of them use styrofoam to make up the bulk of thier structures and use a thin layer of mortar/plaster to add detail.

I made mine with the lightwieght concrete mix to avoid having to go through histronics to keep the structures from trying to float to the top of the tank. It also allowed me to design a lot of caves into the background which imo becomes more difficult when using styrofoam. Down the line sometime I will have to recoat my tank and these structures are easily removed without having to scrape silicone off the tank. The recipe for my concrete mix is at the begining of this thread.

So far as a sealer I believe that Lomax used clear fiberglass resin to cover the structures for his diy 600g tank but was dissapointed by how it changed the colors of his background. If your not keeping soft water cichlids it shouldn't be to much of a problem as the background will eventually seal itself with algae and bacteria. This is my plan anyhow. While doing my fishless cycle I'll also be running my light system to encourage algae growth.

You could also go ahead and make the background and cure it outside the tank. This will allow you to get your fish into thier new home untill the cure is done. Then it's just a simple matter of temperarily housing the fish in another tank or bucket while you put the background back in the tank.


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## iceblue

Done.......finally. The next time I build one of these it will be on a much smaller scale. :lol: 
I'll start out with a list of the materials I used and then explain how they were utilized with each pictured step.

1 gallon SikaLatexR. This is an excellant concrete bonding adhesive and acrylic fortifier.
1 bag each grey and white thinset mortar. (silicate dust warning)
Quikcrete concrete color. Charcoal, brown, terra cotta, and buff.
Disposable 3" brushes.
Various size cheap round artists brushes.
Water spray bottle.

The first step was covering the whole project in black(charcoal). This took 2 coats using the charcoal color and acrlic fortifier mixed with grey thinset. I first mixed all the ingredients to get the consistancy of liquidy paste. Here, as in all other color steps afterwards, I allowed the mix to sit for a few minutes to get a false set. It will thicken up and seem like it's setting but if you give it a swirl with a stick it'll loosen up. At this point, if need be, I added water from the spray bottle to get the consistency I wanted for application. It should also be noted that the concrete color has a saturation point. Adding more color will neither make it darker nor more intense. Just make sure to use enough to reach that saturation point and use carefully measured amounts when mixing colors together.
For this first overall coat I used a consistency of slightly wetter then melted ice cream...... or maybe more like transmission fluid. :roll: 








For the second step I used the white thinset with just the acrylic fortifier. This was applied with the disposable brushes that I modified with scissors to make gaps between the bristles. As the stripes were being painted on and the brush was running out of paint I "dry" brushed the areas in between the stripes.








For the next step and all others afterwards I used only grey thinset for mixing. Here I used the brown, terra cotta, and buff concrte colors to cover the white "stripes" and make sectioned areas leaving black and white dry brushed areas to seperate the colors.....Was not real happy with the results here, but more about that later.








Here is where I started useing the artists brushes. I applied dots of color ( with apoligies to Seurat) mixing the terra cotta with brown and the buff with brown in various proportions. While doing this I desperatly tried to cover the intensity of the picture above.








More dots of color but this time using brown mixed with charcoal in a couple of different proportions. By this time I was pulling hair trying to tone this thing down. :lol: 








I finally decided by this point to make a glaze of black and brown to darken the whole thing even further. This was a very liquidy application but it did give me the final look I was wanted. Both to the left and right of this picture are what the stuctures looked like before the application of the glaze...............This was a leap of faith for me.








Close-up of the final product. I sprayed it with water to see how it would look underwater. 8) So, so happy.  8) 








I can't wait for my fishies to be dancing under the moonlight. :thumb:


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## bentcountershaft

Looks sweet! Congrats on an great looking tank. I'm sure it was a lot of hard work, but the results are worth it.


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## chefkeith

Great job on the caves. Looks amazing.


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## iceblue

Bentcountershaft wrote:



> Looks sweet! Congrats on an great looking tank. I'm sure it was a lot of hard work, but the results are worth it.


I got a crick in my neck reaching in to make and paint this thing but yeah it was worth it. 

Chefkieth wrote:



> Great job on the caves. Looks amazing.


Thanks. Thier are a total 0f 40 caves with 52 entrances. Thier different sizes and configurations so thier should be something for everybody when I finally stock it. 
By the way, hows the river tank doing?


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## remarkosmoc

awesome!! :lol:


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## chefkeith

iceblue said:


> By the way, hows the river tank doing?


There are just a few aesthetic glitches with it, but otherwise it's doing great. All the work put into the project was worth it. The fish love the caves in the foam/concrete island and the water flowing around it. 
I look forward to building another someday since now I have a better idea of what I'm doing.

I really like some of the construction ideas you had too. This is probably the one of the most amazing projects I've seen.


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## iceblue

Thank you for the compliment and I know what you mean about looking forward to doing it again.

I found very little information on the web about perlite concrete projects before I started. One of them was for building a small kiln out of a coffee can to smelt metal and others on how to make lightwieght parking structures and a kayak. It kinda felt like I was on my own with this. I know the next time I do it it will be a little different.....Just a wee bit wiser now. :lol:


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## chefkeith

Not having instructions is what makes it fun. I learned more about mixing concrete from my project than I probably would of working in construction for 20 years.

I didn't see much info about making lightweight concrete either. I do remember that Perlite soaks up water like I couldn't believe. I'm glad you found a good mix for making the lightest non-bouyant concrete possible. I'm going to steal that recipe and some of the methods you used for building extra caves for my rivertank. I'll have to start up my old thread again soon.


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## iceblue

When I first started experimenting with different mixtures to come up with the one I eventually used I had to choose between perlite or vermiculite. I placed a handfull of each in seperate containers of water. The vermiculite really sucked up the water and actually broke down into clay. I noticed that its expanded stucture looks stacked plates and once wet will squish without much preasure. Didn't seem like a good choice for submersion. The perlite on the other hand absorbed some but a lot of it still floated after a couple of days. Its basically expanded glass instead of mica like the vermiculite and became my aggregate of choice.



> a good mix for making the lightest non-bouyant concrete possible


Actually the mix I used was real close to bouyant. The skin of mortar and sand that I put over it is what keeps it heavy enough to sink.

Are you going to make rock structures to fill in under your "roots"?


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## chefkeith

I fixed that problem under the roots by adding waterfall foam around the top of the island. The center braces hold down the island.










I want to make some rounded corners/caves out of the lightweight concrete. Right now, I'm using a quartered bucket in some of the corners, but they don't stay in place too well and are ugly.










There is plenty of space in the corners to make something nice and to improve the water flow.


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## iceblue

Chefkieth wrote:



> I want to make some rounded corners/caves out of the lightweight concrete.


I found the corners of my tank to be the best place for making my caves. Plenty of room to design different shaped fish shelters.

Just a little tip, whether it works or not hasn't been tested yet in my tank. I gave the bottom of my caves a slight slope. A little higher in the back sloping down towards the entrance. I figured the fish swimming in and out of them would help to keep them clear of detritus.

You see it asked a lot on the Forum about the leaching of cement raising the water hardness and Ph. I'm pretty confident my long cure time and the acrylic fortifier I used to color my structures will make that nearly nill. Since as far as I've been able to tell you were the first here to try a lightweight concrete mix maybe you could give us clue if a solid lightwieght concrete structure has had any long term effects on your water quality. http://www.cichlid-forum.com/phpBB/view ... &&start=75


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## chefkeith

The tip does work. My main cave is on a slight incline and it has stayed absolutely clean. It's been about a year and I haven't had to clean the cave once.

There was alot of leaching at first, but once the concrete got a biological layer on it, the leaching slowed down. After a few months the leaching was minimal. It's been about a year now and there isn't any noticable leaching. I test the TDS almost daily and it don't go up by more than 2 ppm daily, but the TDS goes up mostly due to the fish waste and driftwood decaying. I have about 200# of driftwood in my system right now.


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## will74

I used this coloring for my 125, which isn't done yet and was wondering if the iron oxide in the coloring leached out into the tank and caused any problems? I didn't think about it harming the fish on a long term basis, anybody know if iron oxide, which is basically rust would harm the fish on a long term basis?


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## iceblue

will74 said:


> wondering if the iron oxide in the coloring leached out into the tank and caused any problems?


You certainly got my attention.  I did some searching and found that "natural" iron oxides as is found in the liquid concrete colors are non-toxic mineral salts that permently fix color to the medium you are using. There is only, if any, small trace amounts of metalic irons in it. Normal routine water changes should be more then enough to take care of anything that might leach into the water.

Thanks for freaking me out. :lol: The search I did makes me feel better about the whole thing. :thumb:

http://www.mme.state.va.us/DMR3/feoxide.shtml
http://www.ci.tucson.az.us/arthazards/paint1.html


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## RiftCichlids

I would like to see how your tank looks with the finished background, any chance for some photos?
I'm glad I ran across this thread and your recipe for lightweight concrete, I had something like that in mind myself. Where do you buy perlite?

Is there anything about the construction you would do different?


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## iceblue

I bought the perlite at the Home Depot. They have very large bags of it for less then $20 in their gardening department. Usually inside.

Things I would do differently.

1. Use half the sand I recommended for the perlite mix. I like the way the added sand helped to form the structures but found it works just as well with half as much. The original formula is on page 1.

2. Spent more time sculpting the structures after I put the skin coat over it. I think it would have looked better with a harder more angular facing.

3. Not go so color crazy.  But this I can change.

4. Make a couple of the structures in 2 pieces instead of one. Although it's a lightweight concrete mix it's still a concrete mix. It's about 40% lighter then regular concrete but 2 of my pieces still weigh close to 90 pounds.

5. Not base my overall design on how my filter system will work. This limited what I could do but. should make for an almost maintenance free tank. ( Will still do those weekly water changes)

My digital camera seems to pick up more color then what it actually looks. The structures to the furthest right of the picture is what the overall tank background looks like to the eye.


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## RiftCichlids

Here is an interesting link that shows the construction of a huge tank along with a concrete background. Click on Mega tank and scroll down for the background.

http://www.freshwaterstingray.nl/Frames ... nglish.htm


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## iceblue

The links not coming up for me.

Edit: Found it. http://www.freshwaterstingray.nl/1Engels/Mega_tank.html

My tank's just a wimpy 350g. Would love to do something like that though.


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## RiftCichlids

Wow, 90 lbs., those are some pretty heavy sections. I wouldn't want one to slip out of my hands putting those sections in my 240 G. tank.

When you tried it with 1/2 the sand, was the weight of the concrete about the same as water? That would be perfect, easy to keep in place without the added weight. I was thinking of making my background in layers that would interlock together as I stacked them. Maybe build it laying flat on a table inside a frame, one piece at a time, wrapping plastic wrap between sections as I build them to keep them from sticking together. Could use pieces of pvc pipe for dowels to hold the sections together.

Fairly large diameter vertical dowels would remove some of the weight of concrete, and could be used as passage ways for UGJs that could be directed out the front at the base of the background.
Would have to figure out a way to make them just loose enough to slide the sections down over them easily.

I like your idea of caves in the background. I thought I would try making wide cracks and overhangs along with the caves for the fish to hang out in.


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## iceblue

The pieces that weigh a lot are very large. Most of the other sections weigh between 20 to 40 pounds. Taking out half the sand did lighten it a bit but the bulk of the aggregate is perlite. The perlite mix is already close to being buoyant and the 1 part Portland with 3 parts sand mix that I used to skin the structures gives it enough weight to stay sunk. Even my 90 pound pieces if held underwater would seem light.

I don't think you have to go through the histrionics of adding pipe to hold your structures in place. If you leave trenches or roughness in the pieces underneath your next section that should be fine for keeping them from slipping around. If you want to lighten them further you could use sand as a filler between your structure walls and wash it out after the structure has dried.

Below is a picture of one of my pieces removed to show part of my UGJ system. Instead of plastic to separate the structures from each other I used thin foam wrapping sheets. I found they make it easier to separate the pieces and make a nice buffer between the concrete and the walls of my aquarium. The foam is stuck on the piece to the right.










Here's another pic with a 1' ruler to give you and idea of the size. The structure it leans against weighs about 20 pounds.


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## jimmymac

Wow Norm! Very impressed!


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## iceblue

Thanks Jimmy.


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## SlipperyPete

I'd love to see some pictures with the fish in the tank.


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## Bungy

Absolutely brilliant - lots of hard work paying off.
Please Please post more pix - im hooked...!!!

Bungy


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## iceblue

I would really like to post more on this but the whole aquarium project is on hold. Times are real tough right now here in Vegas and I'm down to just a single 29g tank with one syno.


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