And best of all, it’s easier than you think.

The materials used for the walls were well researched, mainly from threads on ReefCentral. All materials used in this project are reported to be reef-safe from numerous threads. However, as none of the sources where PhD’s in biochemistry – by following this process you are taking your own risks. To ensure reliable test results, it was ensuresd that all products referenced had been used in tanks for a period of at least 1 year.

All times where the products were referenced had at least one reference to the walls being in the tanks for 1yr or more. The hardest one to find that level of “reference” for was the epoxy… but I did find it.

Mounting Your Rocks

I used Egg Crate and Zip Ties for the Rock. I would recommend using small pieces, the size of the palm of your hand. I found that some of my pieces stuck a bit further horizontally into my tank than I would have prefered. Also, I would recommend using a larger rock and smashing it with a hammer and chisel and using the pieces created. I did this toward the end, and the result was much more interesting shapes. I would also recommend creating “feet” for your wall so that it is able to stand on its own. This has little to do with the tank but so many times when “crafting” I was able to stand the project wall up on its own feet and work for one wall that had feet and it was easier than the other wall that constantly needed to be balanced. Another option would be to working with a friend.

Don’t forget to plan where you are going to mount your pumps to the walls. Create an outline before you start the next step, so that you can work around those areas and leave them clear.

Applying the Foam

Foam used was Great Stuff (red can with yellow cap) from Home Depot. The most important tip here is to make sure to throw down the covering layer quickly. Cover everything with about 1/2 inch or 1/4 inch of foam. You’re looking for the foam to expand within the first 20 seconds to fill in the entire working surface. You’re not going to use too much unless you try. I was most successfull when I used a back and fourth painting motion for the large open areas of egg-crate. This did look like it was going to create ugly ridges for the end-project but do not worry, it does not. Be sure to get under and around the rocks to give them lots of support. It is important to note that you can easily break and rip off excess later and you will not be able to notice any difference once it is covered with sand. Another important tip is to come back after ~20min when there is a good surface crust on the foam (If you touch it and it sticks to your hands it’s too soon, you need to touch it and not have anything stick to you, then you know you are ready to work it). You want to start to flatten the air out of the foam at this point. Work the foam until it is flat, push it in around the rocks and down into the egg crate. 

I was able to complete my project using 4 cans. However, I wanted flat walls with rocks on them, if you want thick walls, use more rocks and still flatten the foam. I’ve hear of people having issues with walls floating, but by adding rocks and therefore weight, there is little chance that your wall will float. My walls were about 20lbs each and did not float.

Resin and Sand

After letting the foam cure for 24 hours, get some Z-POXY Finishing Resin from Zap Glue. I got mine at Dynamic Hobbies here in town. They are on Colonnade Rd. and it costs $20/box and 1 box did my project with a minimal amount left over. I recommend planing your sq. footage and assume that one box will cover about 10 sqr feet. By using the assumption that each box will give you approximately 10 srq feet you will be able to estimate how much to buy. In case you buy a little too much, unopened/undamaged boxes can be returned to most stores.

The next step is to mix equal parts of the resin as directed. It is advisable for spreading the resin onto the walls that a 1″ paint brush is used. It is important to note that the product has a working time of approximately 20min, so it is suggested to work in 1 aqe foot sections at a time, as I did. I recommend Blobbing on the resin, then holding the brush straight up and down, push down and swirl the resin into every nook and cranny, you need this resin everywhere you want sand to stick, so be sure to use a far amount.

Don’t wait too long before putting the sand on your project or else the resin might dry too quickly. For my project I painted for approximately 2-4min, then started pressing in hand-fulls of sand/substrate. Anticipate loosing approximately 90% of your sand, as it falls off of the project, so make sure to use alot of sand. Because I used alot of sand and epoxy on my first coat, I only had to go over the project with one coat of sand/epoxy. Take your time and make sure to cover zip-ties, foam, etc. I also chose to cover some sections of rock with the sand as well. The basic purpose of the sand is astetics, so that you don’t have to look at yellow foam while you wait for coraline and other similar encrusting algeas to cover the foam.

Mounting the Walls In-Tank

Now that the walls are ready for your tank, which has been cleaned and dried, get yourself some silicone from Home Depot. It costs approximately $5.00/tube and I used 1 tube per wall. I do not think you can go “overboard” on the silicone here, get it stuck good and goopy to the walls to avoid dead-spots of water/detritus being created behind the walls. Home Depot sells several different kinds of Silicone. The one you want is a BLUE TUBE with TYPE I on it. It does NOT say that it is safe for aquariums, however it is. The Home Depot guy even pulled out a manufactures guide to the product and showed me that the manufacture even recommends aquarium usage for the BLUE TUBE TYPE I silicone.

Wait 72 hrs for the silicone to dry/cure and bleed-off all of the nasty smell.  That being said, during the first 24hrs, you will have to find ways to push/hold your project to the walls of the aquarium while the silocone dries. Using 2×4’s or scrap wood is one option, but difficult to engineer. There is no easy & cheap ways of doing this. Take the time when you are dry-fitting the walls to your tank to figure out how to support the walls.

Wrap-up

My walls were 24″ tall, by 26.5″ long (approximately, 4 square feet each). This measurement is good as a reference for how far the materials used in this project can go.

This article was originally posted on the OVAS forum here, by Tim.