DIY rock wall background - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 14 Old 12-21-2008, 07:12 PM Thread Starter
conger's Avatar
DIY rock wall background

Hi all, I followed the steps outlined on a different website to create a rock wall background for my cichlid tank, and thought I would post a DIY thread here in case anyone else wants to do it as well! I can't take credit for thinking this up, I'll provide a link to the original site below... I guess if nothing else, use this thread as evidence that it isn't too hard to do, as someone else followed this guy's directions and got great results!

DIY - Aquarium Background

The background is based on using styrofoam and concrete to create a 3-D background inside the tank itself. Be sure to be patient as you go, it took me about 2-3 weeks from when I started to when I was "finished", as you have to allow time after each step for the stuff to dry properly. Since this is a PERMANENT thing that you are doing, you don't want to mess up anywhere, because you can't go back and take it off .

The following is a list of the materials that I used (I think it's pretty complete):

- lots of styrofoam, both large sheet(s) as well as chunks (e.g. from packaging inside boxes) and balls (e.g. from a hobby shop)
- Quickrete Quickwall fast-set concrete
- LOTS of aquarium-safe silicon
- old paintbrush, or new paintbrush that you don't plan on using for anything else after this project
- gloves! (that can get dirty/covered with concrete)
- Concrete pigments, multiple colors (I used black/charcoal and a reddish-brown pigment)
- a bucket that can be used to mix concrete
- rags
- rubbing alcohol
- spray bottle

Here is a picture of my completed tank, as it stands today . Now follow along to see how I did it!


"To an optimist, the glass is half-full;
to a pessimist, the glass is half-empty;
to an engineer, the glass is twice as big as it needs to be"
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post #2 of 14 Old 12-21-2008, 07:21 PM Thread Starter
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To start with, be sure the inside of the aquarium is totally cleaned. You're going to want to start by covering the back (and sides, at lease partially) with the sheets of styrofoam. Use the following illustration as an example of how I did it, laying on sheets of styofoam the further down I went:

silicon pattern



On one side of the styrofoam sheets, apply LOTS of silicon sealant, especially around the outer edges, but squiggled around the inside as well. You really can't use too much (even if it squeezes out the back when you press the sheet on), but you CAN use too little. Really, its a matter of how much money you want to spend on silicon, and how much patience you have. The goal here is not just to securely attach the styofoam to the back, but to also prevent water from seeping in behind the styofoam once you fill the tank with water. I ended up getting some water back there despite my best efforts, but it's fine... I think you want to avoid having an actual flow of water, if it slowly seeps in when you fill the tank, I don't think there's anything to worry about.

NOTE - once you have stuck the first sheet on, there is NO GOING BACK! Lol. Unless you want to bother with scraping silicon off the glass, which I imagine is just short of impossible. So be sure you measure twice, and place the sheets in place to double-check before you actually apply silicon and stick them on there. Don't forget to leave somewhere for your filter tubes and heater! I actually have little recessions in my background where the tubes and heater fit just right... include those things in you measurements.

Once the sheets are on, its not a bad idea to go over all of the seams with another bead of silicon, just for that added seal/protection.

"To an optimist, the glass is half-full;
to a pessimist, the glass is half-empty;
to an engineer, the glass is twice as big as it needs to be"
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post #3 of 14 Old 12-21-2008, 07:29 PM Thread Starter
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Once the sheets are on, start using the scrap styrofoam and balls to add "bumps" to the background. Cut out irregular shapes, cut the balls in half, and stack them on top of one
another, and cover the background with them. Be creative! If I could do mine over again, I would actually add ledges, columns, etc.. for built-in caves and overhangs. Anything is
possible, this is the foundation of the rock background.

These don't need to be totally "sealed" per se, just firmly attached to the sheets of styrofoam. If you've got kids or a significant other, this is a good opportunity to get them to help if
they want, have them help you cut out rocks!

Once it's all in place, leave it be for at least 24 hours, to allow the silicon to completely cure. If you can stick your head in the tank and not smell that silicon smell, you know you're good
to go. Here's a couple pictures of my tank after this stage:



Notice the notches I left on the right side for the heater to sit in, and also notice how on one side, the left, I didn't completely cover it with background.

NOTE - according to the original directions, the author suggests using "Great Stuff" space-filling foam to help seal the cracks in the background... you can see it in my tank as the tan "lumpy" stuff in all the corners. I personally would not recommend using that stuff: (A) it's almost impossible to get a good seal with that stuff anyways, and (B) unless you sand it heavily with sandpaper to rough it up, the concrete will not stick to it AT ALL, and it will be tough to not have exposed parts (undesirable!). So take that as my personal experience with it, and suggestion to you.

"To an optimist, the glass is half-full;
to a pessimist, the glass is half-empty;
to an engineer, the glass is twice as big as it needs to be"

Last edited by conger; 12-21-2008 at 07:32 PM.
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post #4 of 14 Old 12-21-2008, 07:39 PM Thread Starter
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Alright, so now you're committed to the project! Once the silicon is totally cured, you're ready to move on
to putting concrete on this bad boy :). You'll do it in at least two layers (more if you really want, I used
two). Before you start, use masking tape to cover the aquarium glass at the edges of the styofoam. The
bottom doesn't really matter, but the sides do. If all else fails, before it dries its not too hard to wipe off
with a damp rag.

So the first layer, you'll want to mix the concrete in a bucket, and make it nice and soupy (not thick). Once
you've got it mixed up, use the old paintbrush and start "painting" the concrete on everywhere. Try to
cover everything... it shouldn't add any "bulk" to the background, just cover all of the silicon with a thin
layer of concrete. You should still see every sharp edge of the styrofoam, and tell that it's just a bunch of
styofoam cut-outs... thats OK.

Here's a couple of picture of my tank after this step:



Let this concrete dry for 24 hours (but not much longer), then get ready for the second layer!

"To an optimist, the glass is half-full;
to a pessimist, the glass is half-empty;
to an engineer, the glass is twice as big as it needs to be"
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post #5 of 14 Old 12-21-2008, 07:47 PM Thread Starter
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Alright, the second layer! This is where your tank will come alive :). Mix up some concrete, this time
making is really thick. You'll be applying this layer with your hands, not the brush. I'd STRONGLY
suggest using some gloves for this part, because by the end, you're hands will be cut up and you'll have
concrete shoved up under your fingernails. Take it from me .

Now, taking handfuls of concrete, start slapping it on the background, and pressing it in to place using
your fingers. Shove it in to the cracks and crevices, and don't be afraid to apply it THICK and make it
bumpy.. this will make it more realistic. For my 55 gallon, I did about 1/4 of it, then had to add a little
bit more water to my bucket of concrete to keep it usable... Also, take this time to squirt the concrete
you just put on with the spray bottle and water. It will be important to keep it moist for the next few
days, it will make the concrete strong, and also prevent it from cracking as it sets.

Just keep slabbing it on until the whole thing is covered, and looks how you like! Feel free to add
additional layers, all of which should be mixed thick as opposed to soupy like the first layer.

Here are some pics of my tank after my second layer of concrete:



"To an optimist, the glass is half-full;
to a pessimist, the glass is half-empty;
to an engineer, the glass is twice as big as it needs to be"
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post #6 of 14 Old 12-21-2008, 07:52 PM Thread Starter
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after you've got the concrete for the 2nd (or last) layer applied, this is where you'll add any color/pigments that you want. I used two tupperware containers,
and poured the pigment along with water into it. Using the paintbrush (assuming it isn't solid from the first layer of concrete... if it is, use another), I used two
techniques to apply the color: (A) stippling, and (B) flicking and spraying with water.

NOTE - be conservative, the pigment is pretty strong/dark, so a little bit will go a long way. If you accidentally apply too much, you can wash it down with water
before it dries. Also, IT STAINS! Don't get any on your carpet, and if you get it on the sides of the tank, wipe it off before it dries.

So to stipple it, dip the end of your brush in your pigment pan, then jab the rock wall like you're trying to stab it with a sword. Do it wherever you want color
variation, a good place is in crevices and under bumps, to add a shadow effect. Again, another good place for creativity!

The other technique, is to dip your brush in the pigment mix pan, then "flick" it on the background to kind of splatter it. Then, using the spray bottle, spray it
with water, and it will drip down the wall, creating a "dripping" effect on the rocks. Pretty cool!

Once you've applied all of the pigment you plan to apply, you'll want to do one last clean of the tank before the last step! Use a rag to get up all the water/pigment
off the bottom, and be sure that the glass sides are all clean and smear/stain free.

"To an optimist, the glass is half-full;
to a pessimist, the glass is half-empty;
to an engineer, the glass is twice as big as it needs to be"

Last edited by conger; 12-21-2008 at 07:59 PM.
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post #7 of 14 Old 12-21-2008, 07:57 PM Thread Starter
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Once the pigment is applied, keep spraying it with water (six times a day is ideal). At first, be sure you don't
make the pigment run more than you want, but it will dry/set pretty quickly. For the next 3 or so days,
don't put any water in, but keep spraying it. You've gotta keep it wet!

After about three days of manually spraying it, you're going to want to go ahead and fill the tank with
water. At this point, you'll fill it with water, and let it soak for three days. After three days, drain the tank,
then fill it again and let it soak for three more days. Repeat this at least three times (this is the hard part!
You're almost done and you want to set your tank up, but be patient and be sure you don't mess it up in the
final stages). You can toss in driftwood if you have any, but it's not necessary. I also put in some powerheads
to keep the water circulating.

Here's a picture of my tank while it is soaking:


"To an optimist, the glass is half-full;
to a pessimist, the glass is half-empty;
to an engineer, the glass is twice as big as it needs to be"
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post #8 of 14 Old 12-21-2008, 08:04 PM Thread Starter
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After you've soaked, drained, refilled several times, drain it one last time, and now prepare to set up your
tank! Add in your decorations, and fill it up with dechlorinated water to begin the cycle. If you want, you
can monitor the pH of the water to be sure the concrete isn't pushing it out of your desired bounds. I
personally did not experience any of this, my city tap water is at about 8.0, and the pH never strayed from
that. But I wanted to at least mention the possibility of this.

It's pretty important (I think), to use Quikrete Quickwall in particular, as it is a fast-setting kind of concrete
which sets in a couple of weeks as opposed to a couple of months like most concrete. I think it also doesn't
affect pH as much as other types might, but I don't know that for a fact. I just know that my pH wasn't

Here's a couple of pics of my completed tank, the first is the first time I filled it up and decorated it, and the
other is the tank as it is today, the same pic I put in my first post. Feel free to reply with questions!



"To an optimist, the glass is half-full;
to a pessimist, the glass is half-empty;
to an engineer, the glass is twice as big as it needs to be"
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post #9 of 14 Old 12-21-2008, 10:06 PM
onefish2fish's Avatar
ive seen this before, but thats awesome.

im sure there is a way to make one thats a wall that can be inserted as a background instead of a permanent fixture, also you can always take some styrofoam pieces and shave them how you want, cover them in concrete and use them around the bottom of the tank as decorations. you can pile them how you want loosely and they will look as if they fit in with the setting.

anyways, AWESOME!!
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post #10 of 14 Old 12-24-2008, 12:41 AM
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yeah, good work. I don't know if i'd make one permanent either (i like to remodel every now and again).

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