DIY rock aquarium tank background

[Chuckmeister]

This is an old DIY project that I thought I'd repost here. Hopefully it may inspire a few people to have a play with their aquariums.

I’d been mulling over my background on my 8*3*2.5. I couldn’t find any paper backgrounds that were 2.5 foot tall and really I wanted to do something special with this tank.
These backgrounds are really easy to make and I’d recommend anyone that likes to tinkle with things to give it a shot. There are many different ways to do a background ranging from flat if you are limited by space to something like I have done below.

First you will need a few bits and pieces to get you going…..

You will need some cement, expanding spray foam, some cement colouring, in this case red oxide, a couple of nice thick, stiff brushes, some blades,lots of toothpicks and a butane torch to give the textured effect on the foam. In the case of the brushes I found it hard to find something that was stiff enough to brush on the cement. In this case you can just cut the bristles of the brush shorter to stiffen it up a little.

You will also need some foam. I bought 2 sheets of 8*4, 50mm thick items. I had the foam shop cut a sheet into a 8*3 sheet to fit my tank and then into halves to give me 2* 4*3 pieces. You will have to use your judgement as to the correct sizes as I made mine in halves and it didn’t fit. I then had to ‘hotknife’ it into 4 pieces to fit so make sure you have the dimensions properly measured So after I had the backing cut I had a whole sheet (the uncut piece) and what was left over from the backing. I will state now though that I was left with a 4*4 piece (or half a sheet) left over. First I started by hiding my plumbing. In this case the overflow box (top right) and the return (left side) that will be my Jet system that will be installed.
Now the trick to attaching the foam to your background are toothpicks. Just place your foam where you would like it to be attached and hold in place by stabbing the toothpicks through at 45 degree angles. I used lots as the more you stab through the firmer it will stay in place.

I then started on the cave system and base of the background. Remember to cut holes in the supports as this will allow water flow through and prevent dead spots. It will also allow your fish to frolic between caves

If you break anything, no worries just pin it together and you can spray a little foam over it later to join it again. This and the cement you will coat it with will be ample.

This is how it looks with the bracing and top of the base on… note - everything is pinned on…

Then I made what will be my caves on the bottom of the structure. Most of this was scrap left over. To this stage I was still on the single sheet first sheet of styro. This includes the 700mm sheets on the back, so the 500mm left over basically got me here. It was then time to put on a few ledges…..

Remember that it doesn’t have to look too pretty as you’ll see later in the article….after the burn… I then put in some ledges and overhangs…

and this is a shot at the end of the night of the complete backing, stuck together well with several hundred toothpicks…

I’d also like to note that this produces lots of styro mess. This is after about 3 buckets of foam swept up so if you do this inside like I did make sure you have a patient partner Like I luckily do (sometimes)

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[Chuckmeister]

Now this is where it all starts coming together. You will need to grab one of your cans of spray foam and start joining everything together. Do everywhere….top,underneath down the joins and seams everywhere. It will look fairly ugly and you will think that you have taken a step backwards or done something wrong. Dont worry about it because the cement stage pulls everything together. As you can see in some images, I had foam drip by accident onto the piece. Just let it as they just look like small rocks when the concrete goes on. In fact I added small blobs onto the back and base just to add more texture.

This is where I found my mistake that the two halves did not fit. I had to get an old bread knife,heat it on the BBQ and cut it so that I had quarters. It was a silly mistake caused from too many bevvies in the planning stage
Anyway before I got onto the burning stage I cut and test fit into my tank to check for the final fit…

After the fit comes the burn..
I had 50mm foam so I had a bit to play with. If you have thinner foam, a little caution is needed as it melts quickly. Dont be shy though and burn in indentations etc. The ledges will shrink and twist a little and by the time you have finished the background looks considerably different to the perfection you had initially built. Again dont worry too much. In fact I burnt a few holes on the top of the base. I consider these a benefit as now my fish will not only be able to swim between the caves but also up through them as well. Just don’t make the holes too big and you also dont want to burn any holes in the actual backing. Definitely don’t want to see the back of the tank….

Now that is done, its time for the final cementing. This is the most time consuming though I guess for a smaller tank its not so bad.
Just on a note about the concrete mixing for anyone interested. I mixed a 4 to 1 ratio of sand(4) and cement (1),mixed in the binder/sealer into the water and made a fairly sloppy mix but not too thin as to make it watery.
The binder is not needed if you don’t want too and in fact I dont know if there will be any repercussions yet.
You can also put in a few drops of dish washing liquid into the mix. This will help make a more creamy mixture like a render.
There is no set way to apply the cement though a little playing around will soon show what you like. I stippled all my coats and this gave quite a textured finish. Brushing it on will give a smoother finish.

I put on three coats of cement all up leaving half a day to dry between coats. The second coat I lightened the colour somewhat to hopefully resemble more closely the Woomera red rock that will be used forward of the background. You may tint up your cement lighter or darker if you want to add shadows and features but personally after viewing other peoples I dont think it makes much difference after the establishment of algae etc but hey its your creation, do as you will

The toned up colour

And a final shot with the Woomera rock that I will use..

also just on a final note that the back of the background facing the glass is not cemented or sealed. I hope that you guys are not daunted by this if you are interested. It really is extremely simple and a background the size of mine only takes a couple of days at most. I’d like to see other peoples as its a bit of fun and takes away some of the seriousness that can sometimes consume the hobby.
and just quickly on Price…. the foam cost me around 100 dollars though I had half a sheet left over and the materials cost maybe around 150 dollars. All up around 250 bucks for a fairly kick butt background and a bit of fun making it.

and to wrap up...some finished shots. these are not current though I still have the tank and background.

Chuck

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[Donny Brasco]

looks pretty damn epic man i love it, and i love diy 3d backrounds, i have all the stuff sitting there waiting to make some for a few of my different tanks.
One step i noticed you skipped or maybe forgot to mention is that you need to rinse the tank with the background for about a week and keep flushing and topping up as the cement will leach into the water raising the ph very high.
one other step i will take also is i bought some clear pond sealer which i plan on giving the whole background one or two coats before putting it in as well just to be sure.

but job well done man it looks awesome

[LexyBoi]

Love it [emoji173]️

[Ged]

Chuck thanks for posting this very informative DIY. There is a number of different ways of constructing these background and I found this one very easy to follow. The finished product is outstanding and very natural looking. You would pay a fortun for a commercially produce background.

I have used a transformer and a piece of wire strung between timber handles to slice through styrofoam.

How much do you think you think the finished product weigh when completed.

[Mattzilla]

looks really good mate