# concrete backgrounds? whats the problem



## davenoble (Jul 7, 2009)

right, im after making a 3D background myself. as im a carpenter it shouldnt be too tough.

but i have a few questions.

1) what can i use instead of concrete that is completely inert and wont affect water?
2) i plan on fitting it whilt the tank is half empty. (i know its possible, before you lot dive in)
but should i leave it half empty for the silicone to dry?
3) and last of all, where the farook do i start?


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## gnomemagi (Jun 13, 2009)

To 1, I know some people have used something else to coat with, but can't remember offhand.

2) Silicone will cure and seal underwater - a urethane based sealant will as well (I don't know if those are safe for fishies).

3) Buy some foam and start chiseling.


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## davenoble (Jul 7, 2009)

gnomemagi said:


> To 1, I know some people have used something else to coat with, but can't remember offhand.
> 
> 2) Silicone will cure and seal underwater - a urethane based sealant will as well (I don't know if those are safe for fishies).
> 
> 3) Buy some foam and start chiseling.


hahaha, as for number 3, im a carpenter and *** turned rough items into smooth items for years, im not so sure as how to do the reverse of this, IE, how do i make it look like a rock


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## mightyevil (Oct 23, 2008)

You can use Drylok to seal the background, the drylok comes white, its like paint. You may add concrete dye to add color, that is how I made mine. There are many different methods for creating rock shapes. My favorite would be melting the styrofoam. I used a soldering iron to shape mine and I can't complain about it, looks nice IMO.


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## davenoble (Jul 7, 2009)

mightyevil said:


> You can use Drylok to seal the background, the drylok comes white, its like paint. You may add concrete dye to add color, that is how I made mine. There are many different methods for creating rock shapes. My favorite would be melting the styrofoam. I used a soldering iron to shape mine and I can't complain about it, looks nice IMO.


may i ask what drylok is? and as we live on different continents, i may not be able to get it here, so is it similar to any product that you know of, so i can decide if there is a uk equivelant

thanks


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## Tinga (Nov 27, 2009)

I just picked a gallon up at my hardware store for about $20 US dollars.


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## newfisher (Dec 20, 2008)

1. See this for drylok: http://www.ugl.com/drylokMasonry/masonr ... /latex.php
An alternative to drylok is epoxy. I mixed earth-based pigments to the epoxy and sprinkled sand of different colours and grain size to the wet coloured epoxy on my background to give it a more realistic finish.

2. I would be very cautious using silicone where there are fish. Type I silicone gives off acidic acid gasses as it cures, with the likelyhood that some will become dissolved in the water even if used only above the water line. Therefore, watch your pH.

3. I've completed my apprenticeship in cabinet making, and I'm a geologist, so I might be able to give you some hints on carving your background. You could go for a "rock pile" look. Or you could go for a "bedrock outcrop" look. For the latter, study road-side and/or shoreline bedrock outcrops, should there be any in your area. Most road-side outcrops are a result of blasting and will be much "fresher" with sharper edges on the rock breaks and faces. Shoreline outcrops will have been subjected to a much greater degree of erosion and will be much "rounder" in appearance. Anything in between should be good for a background. Take photos, or seek bedrock outcrop pictures on the Internet. Be aware that at the outcrop scale, bedrock bedding (if you're trying to reproduce sedimentary rock) will be mostly in one orientation. The same may or may not apply for igneous or metamorphic rocks. At the outcrop scale, fractures and joints in bedrock typically occur along one or sometimes two orientations and all "cracks" will be parallel to those main orientations. Fractures may or may not cause offset in the bedding or other jointing. Fractures may occur at a rate of 1 every 1 to 2 metres, or at the cm scale in the case of fracture zones. The world is open to you in between. Try to apply these basic principles and your background will look more natural. As for carving, use saws, knives, or glue up foam panels into the shapes you want. To "weather" the background (round over the rock edges), use an electric heat gun. Some use open flames, but that's more risky and much more difficult to control. Hair driers are not hot enough for most foams.

**** luck!


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## mightyevil (Oct 23, 2008)

Tinga said:


> I just picked a gallon up at my hardware store for about $20 US dollars.


Yeah that's it...

Dang! I got that for $40, stupid franchises!

Davenoble, you gotta look for some type of masonry waterproofing latex based product like the one on Tinga's picture. Maybe you can order from here if you don't find it over there? Good luck!


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## Mcdaphnia (Dec 16, 2003)

Epoxy can melt styrofoam. From some projects I've done it looks like Drylok can too, but unless the coating gets detached, you won't find out. Be sure to make it thick using two or three coats. I only used one on the projects that peeled. Drylok is a product for sealing leaking concrete and masonry walls. You probably do have equivalents. It's just the same name is on something totally different, and the identical item is renamed. For example, I have a box of what I'd call Band-Aids I brought back with me from vacation, for a few nicks from the Great Barrier Reef, but the box calls them Elastoplasts.


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## newfisher (Dec 20, 2008)

Mcdaphnia said:


> Epoxy can melt styrofoam.


You may be confusing epoxy with polyester resin?, which WILL melt styrofoam. Epoxy will only melt styrofoam is it is a low solids mix (contains solvents). But hi solids epoxy such as West System, East System, or equivalent products, WILL NOT dissolve styrofoam. The epoxy curing process is exothermic (produces heat) and can be a problem when curing large masses of epoxy, but the temperatures generated from thin film applications, such as on a background, are not high enough to melt foam.


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## Mcdaphnia (Dec 16, 2003)

You know, all this about sealing concrete away from contact with the tank water is not all that significant, except for low pH loving fish. Color and texture are something esthetic that can matter to us. But if the concrete looks natural enough to you, it is going to seal over naturally within a few weeks and not really affect the water hardness or pH except in extremes such as very soft low pH water.

If you are keeping rift lake cichlids or Central American or Malagasy cichlids that come from limestone areas with hard alkaline waters, the concrete will be a taste of "home". Reef keepers build their artificial stonework with concrete and try to find a mix that will be very porous. While in freshwater you are not going to create a vast and varied population of macroscopic fauna inhabiting the pores inside your background, it would still have a valuable microscopic population that could inhance water quality and provide first foods for small fry. Painting and sealing the rock will reduce that option.


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## R-DUB (Jun 3, 2007)

I uderstand why salt water BG makers use concrete. I do not however understand why freshwater BG makers cover them in crete. Or even resins or epoxies. Both are hard to work with and give no real advantage that I can see. Cover them with Drylok!! Easy to work with, sticks very well to styro, doesnt hide detail, doesnt change water perimeters, can be colored to your liking, easy cleanup, cheap, reliable what else do you want?? Try it you will be glad you did! I am very glad I used it. ( My way to hide overflow towers) Check out my post. It has been in my tank sice July and not a single problem. Good Luck!
:thumb:


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## Mcdaphnia (Dec 16, 2003)

R-DUB said:


> I uderstand why salt water BG makers use concrete.


I don't know of any saltwater BG makers. They are making artificial rocks to stack together and want something porous with lots of surface and interest, that will stack ina stable, tied-in configuration and support pieces of corals (called frags, from "fragment") and entire corals. Yes the completed pile looks similar to a background, but it has a different philosophy. It's an environment, a biological filter and a refugium for small life forms that help keep the tank stable and clean. No reason that would not work in freshwater too.


R-DUB said:


> I do not however understand why freshwater BG makers cover them in crete. Or even resins or epoxies. Both are hard to work with and give no real advantage that I can see. Cover them with Drylok!! Easy to work with, sticks very well to styro, doesnt hide detail, doesnt change water perimeters, can be colored to your liking, easy cleanup, cheap, reliable what else do you want?? Try it you will be glad you did! I am very glad I used it. ( My way to hide overflow towers) Check out my post. It has been in my tank sice July and not a single problem. Good Luck!
> :thumb:


I've used Drylok, and it does a good job of sealing and covering things, but it does seal and that is true of the paints, resins, etc. Not sealing it up, can make it more useful and create a healteier environment than without the unsealed rock. Nature will seal away any harmful source of high pH, if you use common sense and "cure" concrete in the submerged stage with as few water changes as you can.


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