Foam reef background


New member
Hi all,

Being inspired by Kannin's thread, my wife and I started working on our own foam wall for our 70g reef.

We don't have any base rock laying around, so it's really just the background, but it's turning out awesome. Just thought I'd share the progress thus far:

A couple of the pieces all foamed up. We were originally going to do the back wall, the overflow, and one side of the tank. We have all the pieces, but have since decided to only do the back and corner overflow.


Here is a closeup of one of the pieces. While the foam was still wet, we sprinkled on some sand, just to give it a little initial texture. Once the foam is dry, the sand is permanently attached. We also poked in a few short pieces of PVC, so we will have some mounting points for frags should we decide to use them.


We were going to install some 90deg PVC elbows onto the sides of the overflow for mounting points, but we forgot to ziptie them before the foam, and they just wouldn't stay in the foam alone.

Coincidentally, I discovered a cool way to disguise intank plumbing. Just use the Great Stuff foam and roll your PVC in it. Once dried it has a really cool "rocky" texture and I think it would blend in a bit better. I'll see if I can get a picture of this later.

We had to do the project in a couple pieces in order to get them into the tank. Because of this, we had to trim away a few inches of the overflow foam, and then use some trickery with saran wrap between the pieces and in the tank to fill in the voids and make the pieces match up.


So this is how it sits at the moment. Hopefully tomorrow we can take the pieces out of the tank (and hope they come apart nicely and fit back together) and start applying the epoxy. We're using the same "20 min finish" epoxy that Kannin used in his thread. We will apply it to all foam surfaces, and then sprinkle more sand on the pieces. Once this is done and cured, we will silicone everything in place.

Don't mind the piece of wood and Pepsi box...that was just to get everything staying in place. The pieces seemed to have warped a little bit over night. They weren't on a very flat surface when we made them, and it was super cold in the garage, so that could have something to do with it.

The tank has a glass overflow. The foam piece covers this and eggcrate extends all the way to the top of the rim. But the foam "rock" stops short of that, hiding the glass, but the overflow stays functional and it gets a built in strainer. I'll have to get a closeup of that eventually.

By the way, I wouldn't lay your eggcrate on cardboard and then's really tough to get off.

Anyway, that's all for now.



In Memoriam
I have never seen this done before. More pics please!

This may lead into a new forum all of its own.
Theme based reef tanks?
I always wanted to put all the WORLD OF WARCRAFT characters in a fish tank.


New member
thanks for sharing this, what kind of foam do you use? and what kind of epoxy are you planning to use, where to get it?


New member
I used Great Stuff foam in the red can. You can get it at HD. Only problem is I used up like 5 cans of the stuff (did the background, overflow, side wall, and a test piece). The black can expands a LOT more, and I kind of wish I had used at least one can of it. I have some fairly deep parts that I could have used a lot less foam on had I gone with the black can.

The epoxy I will be using is the same stuff Kannin used.

except mine is rebranded for Hobby Town USA, where I got mine. Some people have recommended Z-poxy by ZAP, which Hobby Town also had, but it is way more expensive.

You can also use plain old Bondo brand polyester resin used for fiberglass work. You can get it at HD near all the glues and stuff. Only problem with that stuff is it's REALLY stinky, and you'll need to let it cure for a week or so till the smell goes away.


New member
Just out of curiosity, are you worried about the pieces floating? Or do you have a way to tie them down? I'm hoping to go along this same route when I start my 180 build and love all of the new ideas that keep popping up on here. Looks good btw.


New member
I am a little worried about them floating. I am planning on attaching them to the glass with lots and lots of silicone, but I am also thinking about attaching a bottom "shelf" to the pieces that would run underneath the sand and rock.


New member
If you can wedge the top in under the lip of the tank and then use pieces of egg crate that run from the bottom of the reef wall... out to the front pane and sylicone them to the glass (under the sand) it'll hold. It's how I got mine to not float. Oh.. I also used 150 lbs of rock. Maybe that's another reason why it didn't float.

It's lookin' good.


New member
Thanks Kannin. I think I will try running a piece all the way to the front and siliconing it down. It's not quite high enough to wedge under the top frame, since I had to cut the eggcrate down a bit because of the thick bead of silicone at the top.


New member
We did some epoxying last night. have the back and sides of the main piece done, and have the whole overflow piece finished. It looks pretty good with more sand attached. Might have been nice if we had the sugar-sized sand, but it's no big deal.

Sealing the back and the cut sides sucks up a LOT more epoxy than the smooth front surfaces, just in case anyone was wondering. I think the project with use up probably an entire 13oz bottle of epoxy. We bought a 6oz bottle as well, but hopefully we don't need to crack it open.

Will get pics tonight.


New member
Just about finished up here. A few pics.

Everything trimmed up and siliconed in place. Got a basic layout for my DIY base rock. I have about 30lbs of cured LR that will go on top of this:

Added the sand. Might be obvious that the sand used on the foam background was the same as used for the sand bed. It's not quite so obviously the same in person though.


A side shot:

That's all for now :)


New member
<a href=showthread.php?s=&postid=12316278#post12316278 target=_blank>Originally posted</a> by widefx
Nice Rock :)

Haha, thanks Denny. It turned out really nice. Had to break up one of the pieces because it was just too big. I think it'll make a good base to build a rockscape off of.


New member
Lookin real good jason. I love the idea of using the eggcrate for the top of the overflow. Is the black spot in the top middle of the tank the return? Can't wait to see it filled.


New member
The epoxy serves a few purposes: 1, it gives something for the extra sand to stick to. 2, it helps protect the foam from any UV light present. 3, it helps seal it from the water, which could possibly damage the foam over time.

The spot in the middle is the return. eventually the return will be over the top and that will be the feed for a closed loop, but that is a ways off.

I had to cut the eggcrate at the top of the overflow stuck above the lip on the rim and my glass tops wouldn't sit flush. So now it's just one row of eggcrate, which still should be enough. We'll see how it all works out when I get around to putting water in it.

Thanks for the compliments everybody.


New member
Looks great, and is actually not overkill like many of the rock backgrounds I see. Thanks for keeping us posted


New member
Very nice Jason. I recently finished mine but didn't use epoxy or sand just dumped crushed rock on the wet foam and pushed it in. Hopefully the foam will hold up over time. Your epoxy and sand came very nice.


New member
The biggest problem I've had with my foam background is my tuxedo urchin eating it in his hunt for coralline. I find hundreds of little pellets of the stuff in the sump after he has been on the wall for a while. Just something to keep in mind.