# 3D Background disaster.



## Nathan Shaw (Jun 20, 2014)

I am going to run through a project I tried doing recently which ended in an epic fail.  I thought I would share my experience so anybody who has attempted doing the same might come up with some better ideas, and anyone else who is contemplating doing the same are aware of the pitfalls which I experienced.

I have a 250l tank which I had no background and had part filled with local rocks/pebbles. I was a bit wary as to the rocks as I knew that they literally looked like a pile of stones in my tank and that the more I put in the more precariously balanced each one would become and I was scared that one day they would smash the tank.

I had seen plenty of video's on YouTube and on forums like this showing how people had made their own backgrounds using polystyrene and cement etc.
How hard could it be ?

Over the next few days I will try and document what I did and how it all went terribly wrong.

Here is the tank before I started.


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## Nathan Shaw (Jun 20, 2014)

First thing I did was design the background. I didn't bother with anything fancy I just had an idea in my head. I wanted to cover up my external filter pipes, the heater and the internal filter. I wanted to build in some cave type structures and other hidy holes too.

I then bought a pack of polystyrene foam from B&Q Warehouse in Huddersfield and set about cutting it to size.










I was getting really excited at the prospect of building my new background by now :dancing:


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## Nathan Shaw (Jun 20, 2014)

I took the design I had in my head and created a base and a back. With me having to put this into an already established tank, I wanted one that would be free standing.

I stuck two sheets together and cut out spaces for the inlet/outlet pipes. I created stacks of "rocks" and made caves using PVC drain pipes. I covered the pipes in polystyrene and foam, to make them look like natural rocks.









Obviously the square edges of the polystyrene would need rounding off etc but it was starting to take shape. Using a marker pen I outlined the shapes of the rocks on the back ready to cut and shape.









Again at this point everything seemed to be going swimmingly although it was a time consuming job. :dancing:


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## Nathan Shaw (Jun 20, 2014)

So the next step was to carve out the rocks and make the polystyrene look like real rocks as opposed to blocks of polystyrene.










this has got to be one of the messiest jobs I have ever done.


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## Nathan Shaw (Jun 20, 2014)

So once I had finished carving the rocks out and all the sealant was dry I was then going to cover it in cement. The plan was to paint on as many coats as I could and then on the last coat add some colours to the cement to add some contrast so as the background looked quite normal. Once all the cement had been applied I would thoroughly rinse the background then using pond sealer to prevent any harm coming to the fish.










Painting cement onto polystyrene is harder than you may think. The polystyrene is not at all porous so you have to put a thin coat on first and go over it quite a few times for all the surfaces to be covered. Eventually as in the picture above I got the whole thing covered. Then it was just a matter of going in every day for the next week or so and putting on another coat, and another and another. :roll:










Once I had used up nearly the full bag of cement I thought it would be time to add some colour. As you can see from the top left rock in the picture the black cement colouring was rather strong and instead of making the grey darker just made it go jet black. The rocks at the bottom left though when I experimented with the dye came out more to the effect of what I was after.


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## Mcdaphnia (Dec 16, 2003)

I may have been one of the first to suggest using foam in aquarium backgrounds. It was about the end of the 1970's. I was watching someone who had professionally built many aquarium backgrounds for public aquariums. The problem then was that backgrounds made of mortar and real rock tended to go through the bottom of the aquarium, not try to go into orbit. I thought that a few pieces could be incorporated inside and mostly toward the back and top to make the total neutrally buoyant. If it floated to aggressively, you could carve out some of the foam from the back side. It was not my idea to totally replace all of the rocks, just to counter balance them.

If you are going to cover the foam "rocks" with mortar, they will stick better if you think of it as stucco and either use plastic stucco screen if you can find it, or nylon yarn. The rocks can be wrapped with the same yarn as used to make killifish spawning mops, and connected together with a giant needle that is used for some kind of sewing specialty. The pros today avoid both of these ancient methods, and dispense with real rock cement, and expanded plastic foam completely. They use Fiberglas. You can take a step that way by using sand dampened with Fiberglas resin, and cast it in a paraffin or wax paper lined mold.


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## Nathan Shaw (Jun 20, 2014)

Hi Mcdaphnia, this is some great information. If only I had managed to log onto this forum before I started. 
I did watch a video on YouTube where an Australian guy used Styrofoam to build a base, covered it in fibre glass and then used a solvent to dissolve away all the Styrofoam. What I saw of the project was only a small feature and I didn't think it would be appropriate for what I wanted and I wasn't familiar with any of the materials or where to buy them.

I had seen so many videos using polystyrene and cement that I foolishly assumed that the cement would be enough make the background sink.


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## Mcdaphnia (Dec 16, 2003)

The solvent is gasoline, and the resulting byproduct, a thickened sticky gasoline, is incredibly hazardous. You can use heat to shrink the foam, but the danger of fire or fumes is still high. Carving it out seems the safer more controllable choice.

Making a casting seems easier. You get some beach or dune sand, stir in about a tenth part dry oatmeal (gruel) flakes, and moisten with molasses to make the mold. Make some grooves in the design that will fill in and create a structural skeleton for the background. Line it with several layers of wax paper. Apply the sand and Fiberglas resin mixture in a thin layer from about a third of a centimeter thick to feather thin. You only want the sand moist with the resin. Too wet and it will drip and permanently attach the casting to anything the drip can reach.


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## Nathan Shaw (Jun 20, 2014)

Yeah, these were my fears, especially doing it in my garage, I would probably knock myself out, or worse with the fumes.

To continue with how I did created my background, once all the cement had dried and been washed thoroughly I coated with some G4 Pond Sealant. 
This made the cement covered polystyrene transform into something that actually looked very much like real rocks. I was really surprised and pleased with the look. The colours which I had added blended in much better and I was really impressed with how the background looked. :dancing: :dancing: :dancing:

So I transferred the fish to a bucket, with the plan of getting the background in and doing about 4 or 5 full water changes before testing the water and reintroducing the fish.

Then this happened :










It floated. And when I say floated it was like when you put a polystyrene float between your legs in the swimming pool and no matter how hard you try it still finds its way to the surface. aaaaaaaaaaaaarrrrrrrrrrrrggggggggghhhhhhhh.


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## Nathan Shaw (Jun 20, 2014)

I decided I had to somehow weigh the polystyrene down. I toyed with different ideas and the most economical I came up with would be to hollow out the polystyrene and fill it with cement. Then afterwards cover it with more pond sealer.

When removing the background from the tank I noticed that parts of the cement had started to crack. I assumed that this was where the cement was too thin and that the cement was cracking. I soon came to realise that it was the pond sealer that was seeping underneath the concrete and dissolving the polystyrene.

I first drilled holes into the base around 10mm wide about 2" apart, then I did the same in the back of the background. I then filled them with cement.

It was then as I was maneuvering the background into different positions that it was starting to crack more. I used this opportunity to add more cement.










I spent another couple of weeks adding more cement all over .


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## Nathan Shaw (Jun 20, 2014)

Once I had put another bag of cement into the background I tried it in the tank again. The thing weighed that much I needed a hand to lift it in. As I was lowering it in, more and more of the cement/stroke sealant was breaking off and falling into the tank. Then as I went to take the background out again, it had taken on water and this had then caused more of the back to break away.

This is where I got frustrated and gave it up completely.


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## Mcdaphnia (Dec 16, 2003)

Well there you go. FINI. Maybe you just need a big slab of Poret water filtration foam, and cut groves into it for the design and make it cover the back of the tank. I use them as Hamburg Mattenfilters and in most tanks, Java moss, Hydrocotyle, or Riccia grow over the inside surface so if you like the green look, you don't have to texture the surface to resemble rock.


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## JimA (Nov 7, 2009)

You live in the UK, save your money and hold out for a back to nature background or one from Rock zolid..


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## ilm121209 (Jul 23, 2013)

oh man, im sorry to see this. the pink foam at home depot works way better. but at the same time, you have to glue it down, and then wait untill the silicone is really dry, or it just floats away. to sink, and object has to weigh more than the amount of water it displaces... so, with the foam weighing next to nothing, gluing it down is just about the only option..


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## Nathan Shaw (Jun 20, 2014)

JimA said:


> You live in the UK, save your money and hold out for a back to nature background or one from Rock zolid..


Thanks JimA. I will have a look into this.

Although I have had a look at the Back to Nature Background website, the Rock Zolid. These are nice looking, but they are quite expensive £150 - 300 
Also one of the main reasons for me making the background would be to fit it to my filters etc

I have seen a method of using PVC piping which I am considering. I can used rocks or something similar to weight it down. Might not look as natural, but it will be cheaper and if it works it will probably make me feel better


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## Mcdaphnia (Dec 16, 2003)

Nathan Shaw said:


> .....
> I have seen a method of using PVC piping which I am considering. I can used rocks or something similar to weight it down. Might not look as natural, but it will be cheaper and if it works it will probably make me feel better


 Plastic rain gutter, plastic fence posts, and prismatic light grid for suspended ceilings are alternatives of PVC pipe. Mix or match. Stucco mesh can also be used. Bend it to the rock and ledge shapes you want then cover it with cement or with fiberglas resin and sand. http://www.sailrite.com/Phifertex-PLUS- ... cco-0Y3-54 If you can't find the plastic mesh, coat the metal types with fiberglas resin first, to seal them.


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## Nathan Shaw (Jun 20, 2014)

Thanks for the advice. I have measured up some 65mm square downpipe which I think I will use. They do it in black, so I won't have to worry about having white caves.

My only concern is how to 'paint' it to look like rocks. Once I start I will create a new post and go through the ideas on there. Hopefully this one will turn out somewhat better.


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