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Constructing a 3-D Rock Background for your Aquarium
By Donnie Ponder
Aquarticles.com

Day One August 25, 2003

One of my other passions besides fishing is Aquariums. I have kept fish in just about any kind of aquarium you can think of except for African Cichlids. I spent thirty years or so in saltwater, twenty of that being live coral reef tanks. After a bad fall five years ago and hip and pelvis reconstruction and knee surgery a year after that, the salwater has became a big chore to take care of.. The last straw came recently with the knee having to be operated on again. To make a long story short, I broke down my 110 Oceanic Reef and am now in the process of constructing a 3/D rock background to make my new African Cichlids feel at home. What follows is a step-by-step explanation with photos for how to build your own 3-D rock background.

Materials you will need

- 3" styrofoam, mine was 3" thick x 24 " wide x 96" long
- Silicone in tubes and a caulking gun
- A thin piece of plywood cut to the exact size of the back of your tank
- Assorted knives for carving
- Small butane torch
- Bag of Quickrete (or another brand of quick setting concrete mix)
- Quickwall Bag of Quickrete play sand (or another brand of sand to mix with concrete)
- Bag of concrete color, I used black
- Gloves and an old paint brush or two
- Lots of patience

This was my first attempt at this sort of background so I learned as I went. Below are the pictures of the first afternoon into the construction. You have to remember, I was still on crutches from my knee surgery here and could only stand for short periods without a break.

Above : the three styrofoam sheets I used, purchased for $18.00

I decided to build the background in three pieces to allow me to fit it in the tank (there is a glass brace in the middle of the tank). Below is a photo of the left side piece with two layers of styrofoam glued to each other using the Silicone sealant. I used a flat piece of plastic to spread out the Silicone then just laid the next piece on top and weighed it down. It needed to cure for 12 hours before proceeding to the carving.

Gluing the pieces of styrofoam together

Next I began carving on the right side piece after the Silicone has cured overnight. I just used my imagination for a design. On the sides the rocks will vary in depth from 1/2" to 6". I plan on the center rock to be as much as 9" thick. I know this eats up tank space, but I think the effect will be worth it.

The carving of the styrofoam begins

Here is the carving on the left side piece.

Here I am cutting out some styrofoam with one of the knives I used

This photo below shows how the carving on the right side looks after using the Bernzomatic mini butane torch to go over the styrofoam and heat it slightly. Caution shoild be used here as it only takes a bit of heat to go a long way. You could use a hair drier for this. This step really makes the styrofoam look like rocks.

The styrofoam takes on a rocky look after heating

At this point I  had to stop on the project as I decided to make the center piece another layer thicker and I will have to wait for the silicone to cure before any carving is done.

DAY TWO August 26, 2003

Well, on day two of the project I had finished the middle section. Now it was time to check and make sure it fit. Remember the plywood that was cut to the exact demensions of the back of the tank? In cutting and carving the pieces, you use this plywood templet as a guide to insure you are getting eveything the right size. My tank has a glass brace in the middle so I had to make the pieces small enough to fit in between the side and the brace, thats the reason for three pieces. I simply marked the location of the brace on the plywood. You could also draw out the shape of the rockwork on the plywood to use as a rough guide.

My tank after it was emptied and awaiting the background

I built the light hood and stand years ago for the tank pictured above. I coated the whole thing with a special sealant spray, the name of which I can't remember now.

This picture is of the background after completion of the carving and heating.
Note the pieces are a little small, this is to allow room for the cement coating.

Well, that was about it for day two. I was also constructing a biotower in my overflow box for biological filtration and so this took up some time on day two. Coming up on day three, I put on the first coat of cement...

DAY THREE August 27, 2003

On day three of this project I decided to carve one more piece to cover the overflow box in the right corner of the tank. After doing this and using the torch on it a little, it was time for the first coat of cement! I was surprised when I opened the Quickwall that it had fiberglass fibers in it, a lot of fibers. This wasn't satisfactory so I got out a piece of screen wire and sieved the cement and the sand through this wire to give me the consistancy that I was after. The first coat consisted of one part playsand to three parts cement and was mixed thin in order to brush it on. I added a few drops of dishwashing liquid soap to the mixture to make it creamier. The soap will dissapear in the curing process. I used an old paint brush I had and simply brushed the mixture on; it worked pretty well.You will have a few spots that didn't cover well for  this first coat, but don't worry, this is normal and will be taken care of in the next coat. I sat my styrofoam pieces aside to dry and would put on a second coat the next day. Now it was back to the biofilter.

The container I kept my playsand, cement, and tools in out of the rain.

Now we are getting somewhere! Here are the pieces after the first coat of cement

Here is a closeup of the first coat.

DAY FOUR August 28, 2003

It was now day four of the project, and things were coming along nicely. Today I added another coat of cement. This time the mixture was 2 parts sieved Quickwall cement and one part sieved Quikrete playsand; to this I added 1 level teaspoon of powdered Charcoal black cement color. This is a trial to figure out how much color is needed for the third and last coat to get the results I'm looking for. When I mixed this batch up I knew it was going to take more cement than the first coat so I mixed up 10 cups of cement with 5 cups of playsand and added 5 teaspoons of coloring. This produces the formula I mentioned above, but in a larger amount. Each batch I mixed was enough to coat one piece of the background.  mixed this second coat thicker...no brushing here, it was time to get dirty! I tried latex gloves, but ended up discarding them and using my hands, worked much better. you should mix this coat to the consistancy of heavy mud; if its hard to work, add a little water, no soap in this batch. I found that if I wet the piece with a spray mister it helped in the coating process.

I then simply started spreading the cement over the whole thing, sides and all, but not the back. I put a good thick coat on, around a quarter inch thick. I found that I could spread it much better using the palm of my like a trowel. After you get a good coat on the piece let it dry for a few minutes; it will look pretty rough but you will soon fix that!

After about ten minutes or so, take your old paint brush and dip it in water. Sling out the excess water and start brushing the cement. Brush in one direction when you can. Experiment with more or less water on the brush. When you finish, you should have a nice smooth piece of "rock". Below are photos of the  left and right pieces. The piece on the right has a second coat of cement; it looks dark, but it is still wet and will lighten as it dries.

A closeup of the rocks

Here is the middle piece with the second coat

Right side with second coat

One more view

Circled areas were built up using extra cement

Note the highlights in the photo above that I molded onto the rock in this step. I simply gathered up all the mix that spilled on the plywood after coating plus what was left of the mix and molded and shaped in a few humps and bumps here and there and brushed them smooth. It really gave it more character.

Well, that was about it for day four. Oh yeah, one more thing I did in the curing process was mist the pieces every 4 hours or so with water as it was drying; this is called fog curing and will help in the strength of the cement later on. The next day would be the day to silicone the background in the tank. I would have to let this cure before the third and final coat of cement. This final coat would be done inside the tank!

MORE DAY FOUR August 28, 2003

It was late afternoon on the fourth day of the project. I decided that since the second coat was drying so well I would go ahead and Silicone the rockwork in the tank. This would speed things up inside the house. First, with the help of my son and friends, the tank was laid on its back on top of the stand. I cleaned the glass well with Isopropyl Alcohol and then, beginning with the filter box,  I siliconed each piece into place making sure to use plenty of silicone.

Here is the first piece after Siliconing it in place

Heres another view with all rocks in place

A fuzzy view from the front

Another view from the front

It was hard to get high enough to get good photos with the tank on its back on the stand.

DAY FIVE August 29, 2003

On day five of the project, after siliconing the pieces in place last night, I was ready to add the third and final coat of cement. For this coat I mixed just like coat two, two parts Quickwall, one part playsand, and one teaspoon of the cement color. I knew about how much it was going to take to coat the whole thing from the previous coats so I mixed up 30 cups cement, 15 cups sand, and 15 teaspoons of color because I wanted to coat the whole background with one mix to eliminate color variations. This worked out well. With this coat I mixed it heavy just like coat two and spread it by hand, filling in all cracks and gaps between the pieces. I had to stop about half way through and brush it out to smooth it up before the cement setup to much.

This is what it looks like now

Here's another view

Another photo of the front

I let this coat set up for two days, misting it every four hours or so (FOG CURING) then I filled it up with saltwater. I used a 20 gallon salt mix to cure it for three days then changed the water a few more times to get the PH down to normal. I was now finished with the Biotower filtration and the sump was cleaned up and ready to go. I even put in a new return pump while I had it down.

DAY SIX August 30, 2003

It was now day six of the project and it has been about 32 hours since I put on the third and last coat of cement mix. I think the last coat has dried well enough to fill up the tank so I filled her up and added enough aquarium salt to bring the salinity up to 1.020. This should be enough to cure the cement well and set in the color. I just checked the PH and it is running 9.0. I knew the PH would be high because of the cement and the water right from my faucet is 9.0. I will let the saltwater stay in the tank for two or three days and then start changing water. I will empty the tank completely and refill with fresh water. I will do this probably about five times and keep a watch on the PH and other water parameters. I felt I would be  ready for the first test fish in a week or less. I won't be adding any bottom substrate until the curing process is complete. At that time I planned to add pool filter sand and a few real rocks that are pretty close in color to the background.

By the way, the Bio tower I built worked  like a charm. I couldn't see wasting that corner filter and so had to make it useful.

Here is the tank as it was being filled! Note the twenty gallon sump underneath

Another frontal shot of the tank

Note the different shades of color coming from the Aquatinic bulb combined with an Actinic 03 blue bulb. The main lights are not even on, they consist of four 55 watt compact fluorescent lights, these were used on my saltwater Coral Reef . For the deep water effect, I probably won't even use the main lights.

A shot at the left side of the tank with water

Shot of the right side. Note the piece I built to cover the corner overflow

DAY NINE SEPTEMBER 02, 2003

It was now day 9 of the project. After filling the tank with saltwater and circulating it for two days I drained the tank and filled it with fresh water yesterday. I checked the water parameters last night and found that my tap water was very soft with a high PH. The PH was 8.8 and the General hardness was 3 and Carbonate hardness was 4; this means the water is really soft and with the low KH and GH the PH is likely to take wild swings up and down. This is not the best water conditions for African Cichlids in my opinion. I was not really concerned just yet though, because I didn't bother to use any declorinator or any conditioners in this water since it would be drained the next day; this was just another part of the curing process. After draining this batch of water, the next filling would be the last.

I checked the PH the next morning and it had dropped to 7.8. I thought this is where it would bottom out and stabalize when I am finished with water changes.

I went ahead and drained the water again and I just washed my pool filter sand and added it as a substrate. I also added three artificial plants for a little contrast. If I like the plant look, I will add real Anubias and Java Fern to the tank in a few days. I was doing a deep water look and plants may not belong here.

Here is the tank being filled after the addition of the sand and plants, by the way.
I epoxied suction cups to the bottom of the plants to help hold them better,
seemed to work right nice!

Here is the finished product, without fish of course.

I checked the water for a day or two before testing with some feeder fish.

EIGHT MONTHS INTO THIS PROJECT APRIL 21, 2004

I am pleased to update this project after eight months of the tank up and running. I have had no loss of fish and have had several spawnings in the tank! My fish are continuing to grow and prosper in this environment. Most fish are in the four inch range, however, I did add three smaller fish a week ago.This will probably be my last update on this project since everything could not have gone any better. All my water parameters are almost perfect without adding much of anything, just a touch of baking soda and Epsom salt on occasion. If you have any questions on this project feel free to email me. Below are pictures I took on April 21, 2004.

Here is a front view of the tank with its subdued lighting.

Left side

Center

Right side

My Cobalt Blue male

Note: Donnie can be emailed any questions you have at catfishheaven@charter.net