Picture of 3D Aquarium Background

This instructable will show you how to make a cool 3D background that goes inside your aquarium and looks like real rock but only weighs less then a couple of pounds.

Step 1: What you need

Picture of What you need

You will need the following

Razor or Box knife
Foam cutter or maybe electric knife (both are optional)
Ruler or other sutible straight edge
Marker (sharpie)
Tape measure
Caulking gun
Hot glue gun (optional)
Cheap paint brushes, all sizes
Wire brushes
small buckets
Tarp (optional, to keep mess at a min)

1 inch pink foam board (the kind you buy at Home Depot or Lowes)
100% Silicone for caulking gun (GE silicone 1 is what some recommend) I used the Red Devil Architectural Grade.  As long as it does not contain any mold or mildew inhibitors and is 100% silicone it should be fine.  The less ingrediants the better IMHO. 
hot glue (optional)
Cement or cement overlay
Cement coloring (optional)
Small finishing nails

Note on pink foam: There are two types, one has a plastic cover on it (vapor barrier I think?) and the other does not.  I bought the one that did not have the plastic on it.  If you buy the one with the plastic on it, you will have to peel the plastic off.   Also if you have access or want to buy more foam, you can buy several thickness of the stuff to help create different thick and thin layers.  I just used one sheet of 1 inch stuff and glued it together to get the thickness I wanted.

Note on hot glue:  I have read where some people used hot glue to glue everything together instead of silicone.  It is faster and it shouldn't pose a threat to your fish.  I used a combination of both, hot glue on the smaller pieces and silicone on the larger pieces.  Its up to you.  Trying to get hot glue to come out in the quantity I needed on some of the large pieced didnt work.
AsifS818 days ago
Hiii i want to ask that if we use cement for colour so it will harm my fishes or not ?? Did cement can give any harm to my fishes
LaylaT11 month ago

can this be done for salt tank

eatteyah2 months ago

Nice work .. Working with foam by hot water foam cutter really Artistic work and addicted !??

Njxrinzler made it!4 months ago

Thanks for your instructable. I think mine turned out ok. Didn't want anything big, just a nice rock wall. Made a spot on the bottom for my bubble wall to go, as well as a spot to hide my eheim filter.

damionflynn5 months ago

Pulling up an old instructable here. Love what you did. How long did you have it in your tank? Do you still have it? How did it hold up to algae? Did you use this on a planted tank? Fish?

My thought was to create something like this with a planted tank and plant some ferns or something right on to the polystyrene. Curious as to how it will hold up over time though as I don't want to have to pull it out, scrape everything down, and rescape in a year ;)

Would love to hear from you if you still monitor this. Thanks!

Rainh2o (author)  damionflynn4 months ago
I no longer have the tanK, moved on to other hobbies. The wall held up for about a year, I then had an outbreak of black algea, due to some plants I got. The black algea was a nightmare to get rid of. The wall can be scrubbed and cleaned with no problem. It seemed to hold up well before and after the outbreak.
Thanks for the response. ;)
JoeStrout6 months ago

Hey, thanks for this cool Instructable! It's now 4 years later, and I'm wondering, how did it work out long-term? In particular, I'm worried about algal growth, which looks like it would be really hard to clean off (especially if you've glued it to the tank). Did you find yourself with a ruined tank and deep regrets several years later? Or are you still happy with it?

I am curious to know the long term ramifications as well.

jhoule1 made it!5 months ago
I used latex based drylock on mine. I carved it all out of a single piece of foam that comes from the inside of a steel door. ran pipes behind for my canister filter and return for the undergravel jets.

What is the pvc on the bottom of your tank for? Is it strictly for water circulation or is there another purpose?

dafrimpster2 years ago
Latex Drylock works much better than concrete. It is durable and it won't raise your PH like the concrete will. You can tint it with concrete tint powder. It is widely used in the hobby and completely safe.
Rainh2o (author)  dafrimpster1 year ago
I never had a problem with ph. dont know why byt never saw any abnormal spikes with mine
slo5oh Rainh2o1 year ago

Perhaps you used Type V (also sold as Type II/V) portland cement, it's a low PH cement and will greatly reduce any possible PH spike that might normally be seen. Also if you don't use a LOT of cement it won't cause a huge spike but will slowly push your PH higher. There are guys reporting PH as high as 14 in their freshly made concrete "rocks"... that's enough to dissolve flesh.

-I love the idea of a 3d background, but I seriously wonder about all the trapped stagnant water caused by doing this. Perhaps, as some others have done, use a PVC frame for the rear wall and drill holes so you can force water to flow behind the rockwork.

-Do you know if there's any long term effects to using this pink foamboard?

You mentioned Type V (also sold as Type II/V) portland cement. Is this any thing like Ultracal 30 gypsum, it is used for mold making. I have access to alot of it.


bwsandman made it!1 year ago

I loved this idea so i went for it. My concrete did not turn out, it did not stick to the foam but here is the picture of it with the concrete. Not as good as yours/ NICE JOB.

Final Product.jpg
jdtienke1 year ago
I am getting ready to make an insert for my tank this weekend. my question is.... how dirty does it get behind the insert? I know you used a lot of silicone but my design may not need that much. Do I need to worry about getting stuff growing behind the insert?
Rainh2o (author)  jdtienke1 year ago
mine ended witha Brown growth behind the insert, I suspect it's a diotom growth or something like that. I cant see mine unless I look behind the tank but since its up against the wall its no big deal and doesnt get much light back there so it sort of keeps it at bay I think
patrick0002 years ago
Thanks i did it. its nice
Klesa2 years ago
This is an amazing instructible. I simply love it. I am not this talented and I would like to try it some day.
fatmuemoo4 years ago
Hi, I know this post is somewhat dated but I have to questions for ya:
1) How hard is it to keep clean? I know you mention you scrub it occasionally but is that no big deal or does it become an all afternoon event?

2) Do you really have to glue it to the tank? Seems so permanent. Have you ever experimented with other options for keeping it in place?

I love this instructable and i'm thinking about doing it on my 75 gal turtle tank
hi i just read this and i have an idea, first off let me say that your instructable is frakking fantastic and i WILL be using it with a slightly different design to the rock so that i can make caves for my fish to hid in. however i was thinking that although using silicone is probably the best way to make sure your backround never moves and im guessing it would increase the value of your tank by quite alot. however, using styrofoam gives you options for depth, im sure suctuon cups could be added by carving space for them in the back of the foam. OR and im gonna experiment with this, USE MAGNETS. powerful enough magnets could be attached the to back of the foam using silicone and then with another magnet or flat piece of metal could bue used in the outside of the aquarium to secure in place... thats just the idea i had that would probably make it easier to take out/clean
Rainh2o (author)  fatmuemoo4 years ago
I dont really "Scrub" it, i sort of just brush it off occasionally with a stiff paint brush. It only takes about 5 mins of cleaning, like I stated I dont know if you would really have to do this but eventually I would think the algae would build up and look bad otherwise.

Im not sure how you would attach it to the wall any other way except with some sort of suction cup method. I thought about that when I started but with fish, I thought by suction cupping it to the back wall would create a pocket to where fish might get trapped back there. If your turtle was big enough I suppose maybe attaching suction cups to the back of the wall and sticking it to the tank would work.

Another method might be to cut it so it fits the entire height of the back of the tank tightly and then put some large rocks along the bottom, the lip of the tank should hold it down and the rocks at the bottom might hold it in...having it in a turtle tank this way might make it easier to clean because it could be removed. I may have to try this on our turtle tank....
if you glued the pieces together plumb on the back then made it concave like an eighth of an inch on the back and put the suction cups on that you would essentially get rid of the gap in theroy wouldnt you?
Yes, cement leaches out a lot of calcium and raises the pH drastically. Of course, some fish such as African Cichlids like a high pH, but anything over 8.5-9.0 would be too high even for them. Draining and filling is the only way to rid it. DON'T be tempted to use those pH reducers they sell in pet stores. It will only work a short while, then the cement will cause the pH will zoom back up killing everything in your tank. Just a heads up.
Rainh2o (author)  Pseudocrenilabrus4 years ago
OK..thanks...so far no PH spike...but I have changed the water a couple of times so who knows...the Ultra tex stuff I used is only made of portland and sand and nothing else so I dont know if that helps or not...
Portland is what you have to worry about-it's made from lime.
I've read adding vinegar to the change water helps buffer as well?
JD1014 years ago
Do you think you could use planters foam for this type of project?
david547 JD1013 years ago
Planters and florist foams would be OK only after full leaching. They contain salts from the manufacturing process. Talk to your local florist and read the instructions for use. I would do water sample tests on the leachate to be sure it is ready for an aquarium. After leaching you can let it dry before starting the manufacturing process.

A. Grower Wholesaler
splitzwit3 years ago
excellent work...think i will try something like this....if i can get all the resources together...i am living in ireland and priced one of the ready made 3d backgrounds and would of cost me €185...thats when i found yours...
HubertF3 years ago
what did you use for paint/dye to color the last coat of cement?
Rainh2o (author)  HubertF3 years ago
I used concrete tinting you can get along side the quickcrete type cement at the hardware store...a very little goes a LONG way
What glue would you recommend for gluing the pieces in?
And how heavy was the final product?

My only issue with this scale of a wall is that my tank is probably 1/3 of yours, if not smaller (a square 50 gallon, if I remember correctly). Would you say that the wall would still fit in well?
Rainh2o (author)  TinkerWorkshop3 years ago
I started out with silicone but ended up using hot glue for the most of it. You could scale it to what ever size you want or need. I have seen some online (youtube) that take up half the tank...it depends what look you are going for. it only weighed about 3 lbs or so total (total guesstimate)
juicepig214 years ago
I am VERY impressed man! I tried to do this with those white grates that cover fluorescent lights and triple-expanding foam.. It was horrible to work with and failed miserably. I really wish I had gone this direction with it. It would have been stronger and (if I was lucky) could have turned out as nice as this one. I would like to see a pic of the populated tank after a little algae growth and such. It must look great.
Rainh2o (author)  juicepig214 years ago
I just posted some pictures after running this for a long while. Have a coating of algae and stuff on it...I called it aged...LOL...sorry for the cell phone camera photos...hope it give everyone an idea...
I am in the process of making a similar project. I am making a basking spot for my bearded dragon(lizard) out of 1/4" plywood, then i am going to use your method of applying concrete to protect my lizard from the glue used in the plywood... Hopefully it comes out looking as nice as yours!
Rainh2o (author)  nickmccullough4 years ago
Post picts when your done, would like to see it!
ill do that hopefully, will probably be a week or two tho since i only work on the weekends
Rainh2o (author)  nickmccullough4 years ago
Mine took a couple of weeks as well, darn work has to get in the way of our hobbies....
yes exactly, except it is school for me
ihsanadipra4 years ago
i hope can make like this
Looks top notch. Love to see a picture of it with fish and plants added.
makaay4 years ago
Hi bro,
one question in my mind. use cement for color that any side effect to fish.reply plzzzzzz.
Rainh2o (author)  makaay4 years ago
no side effects seen yet. I have a couple of bluegills in there borowed from the pond. Figured if they do good for s couple of weeks I'll put some topicals in.
Looks very professional and real! Very nice job. May I ask what kind of fish you will be putting in?
Rainh2o (author)  Tape-structable4 years ago
My son has a medium sized goldfish he has had for 3 years. I am going to move him into this tank and then get some community fish mates, not sure which ones. I originally wanted cichlids but they dont play well with goldfish. I also plan on planting lots of plants and making it a planted tank, if the goldfish cooperate and doesnt dig things up too bad. Since he will be the only one I hope he is occupied by other things.
Really nice background. I've seen similarly constructed backgrounds online before, but yours looks the best.

You can use expanding foam (Great Stuff Brand) in place of hot glue. It is fish safe. Pond builders use it to secure "stones" when making waterfalls in ponds.

With Goldfish you should consider other cool water fish.

I like the high finned Chinese banded sharks (bad name for a great fish IMO) with goldfish, they are very docile and add a different color / shape to the tank.

Another nice cool water fish that do well with goldfish are White Cloud Minnows-

They are nice fish, visually similar to neon tetras when young and they school quite nicely as well.

Plants will be tuff with goldfish, unless you plant them in pots. Tera cotta work well as do the cheap plastic ones you get from the nursery. A quick coating of Krylon Fusion paint makes them more appealing, and small stones as a top dressing should help disuade the gold fish from digging too badly in the pots.

Plain clay kitty litter makes an excellent aquatic potting soil, BTW.

I would also recommend either Mystery snails or apple snails to help clean the tank. I know some fish keepers aren't fond of snails because they either reproduce in huge numbers or eat all your plants, but these don't eat plants and lay egg clutches above the water line where they can be removed if you don't want babies (they can also be sold on aquatic auction sites like AquaBid.com)

As an aside, perhaps an instructable or explanation of fishless tank cycling would be helpful. I am familiar with cycling an aquarium using straight ammonia and assume this is what you are referring to.

Good luck with your aquarium, it looks good so far.
Rainh2o (author)  underwhelmed4 years ago
Thanks for the info. I'm only going to put 1 gold fish in it. I am going to keep the 10 gal he is in now just in case he tears the plants and such out too much I'll throw him back in there. Those sharks are cool!
Well, with tropicals you would have a much broader palette of fish to choose from.

Very nice, well done. I wish I had your artistic abilities.
Rainh2o (author)  underwhelmed4 years ago
OK..I reread my last reply...Im not ONLY going to put just the golfish in it...I plan on having other fish as well...the stupid goldfish is only going in there because my wife agreed to the large tank if we got rid of the little tank...since the goldfish is the only thing in the little tank then hes going in the big tank and Im going to go with some tropicals, community type fish as well...I dunno what will happen yet. I may end up putting the goldfish back in the 10 gal tank and sticking it over in the corner of the room. This goldfish is actually getting on my nerves, its limiting my selection of fish!!...LOL...I started out wanting Cichlids but they will eat the goldfish and so will about 75% of all other fish I have seen and like...of course if something eats him, I wont have to worry would I?...LOL...he belongs to my 5 yr old so I cant get rid of him...anyhow believe me if I can do this so can you, I have about .0000001% artistic ability and its in my little finger I dont use...
Well he would be happy in as large a tank as you can provide him, but by heating the tank for tropicals he will become stressed. So, I guess it's a bit of a catch 22.

BTW, I'm a forum member at a fish geek site called aquaboards.com, I posted a link to this instructable in their DIY section. I hope you don't mind. I thought it might bring some people here who might never hear about instructables otherwise.

I keep my goldfish outside in a horse trough, I cut and set it into the front porch / deck. It has been running year round for the last 10 years and the goldfish are all very healthy. Much cheaper and longer lasting than a preformed plastic pond.
Rainh2o (author)  underwhelmed4 years ago
The aquaboard word verification you get when you sign up doesnt seem to be working or I am too stupid to make it work. I tried 12 times and gave up.
Sorry about that, the forum changed hosting last week and it has been problematic for people to sign in.

Usually you have to wait for a verification email from the site admin before you can log in. It's sort of tedious, but the owner is trying to keep the forum spamming to a minimum.

You don't have to be a member to read the Forum, AFAIK, only to post or reply.

Here is the link-

Aquaboards and instructables are my must check daily websites, so I was hoping some of those posters might find their way here. It is an older age demo, so maybe not, but stranger things have happened.
Rainh2o (author)  underwhelmed4 years ago
Yeah I couldnt even get to the email verification. I was going to sign up. Belong to a number of aquarium boards but not seen that one. I sent a msg to the admin about it.
Rainh2o (author)  underwhelmed4 years ago
hmmm..never thought about the heat..that might be the thing that makes me NOT put him in there...Thanks for the info!...no problem about the link...I want to check it out...
Using vinigar to clean the glass will allow the silicone to stick better. A lot of the times when silicone gives way, it's because the surface wasn't properly prepared, though it may not matter with this so much. Still, cleaning with vinigar and then wiping it dry with a newspaper (a towel or cloth will leave lint and weaken the joint) will increase it's strength.
Rainh2o (author)  Pseudocrenilabrus4 years ago
Good idea!
makaay4 years ago
why give support ?
Rainh2o (author)  makaay4 years ago
I decided to have a 2 inch space under my background incase I ever get anything in there that burrows, they could burrow under the edge of the "rocks" You will need to support it against the back of the glass until the silicone dries so it wont pull free from gravity
The wet silicone wouldn't be able to hold a somewhat heavy object like this until it's dry. It would tip forward. Of course, after it's dry, it'll never come off. They use that stuff to hold skyscrapers together.
Galt4 years ago
Beauty. I haven't tried it yet but there's a product called spread stone or spread rock that is made out of some kind of acrylic that I was thinking of trying this with. It remains flexible after the cure and can be tinted and all of that, plus you can change the texture from sandy to a kind of almost stucco coarseness...but it's pretty expensive. The company that makes it is called Daich (sp?) and they also make a waterproof primer that seems like it would also help with this and home made tank builds, (the sales rep paints a cardboard box with it at home shows and fills the box with water for the duration and just lets it sit there - very persuasive).

If someones isn't as artistically inclined they can use a CNC to carve a design out of a solid built up block also. I would be really worried about the cement mix leeching though Sounds like you've got plenty of anecdotal evidence to work from so I guess I'm worrying about nothing but I've killed more fish with pH bounce than anything else I've ever screwed up.

I have a friend who sells a commercial version of what you built and they look as good but a background like yours for a 4' 75gal. sells for about $200. Something tells me you ncame up with a significantly less expensive way to create the same effective result. Excellent job. Nice Instructable too.
Rainh2o (author)  Galt4 years ago
PH is usually an issue and most people just rinse and refill a bunch of times to wash it off. When i was contemplating about building an outdoor pond out of concrete I read where you can spray a weak mixture of muratic acid on the concrete to help draw the lime and stuff out, I thought about doing that with this but decided not to mess with it, If i had to fill and refill then I would. At the moment I have two Bluegill I caught out of my lake and they seem to be living it up in there to help boost the filter cycle going. so far no spikes in PH, nitrate or nitrite..
mike854 years ago
Wow, it really looks nice!

Do you think that's possible to create some bigger "rocks" on the wall with cavities to hold some plants. In the case of these big rocks, can the foam break because it want to float? is it a possibility to put some weight between the glued layers to reduce pressure under water? Or perhaps a plastic nail could help, something like that http://t3.gstatic.com/images?q=tbn:ANd9GcRRLhXKYTXT-GelVfik0zfKyEmxa1kM-goXNfEnzUW39IVCt-c&t=1&usg=__GCuYN8nRmNAYoJATt-qD7oQQJgc=

I think it could look like even better (could it?) with 2 or 3 plants on it.
Rainh2o (author)  mike854 years ago
I actually contemplated this idea about plants in the wall. I may try it in a small 10 gal I have. I dont think the floating is an issue. I was going to play with Java Moss on some of the ledges on this one and see how it takes to it.
fgirerd4 years ago
Great project, love the look.
Any idea how this would react in salt water?
Rainh2o (author)  fgirerd4 years ago
No clue for salt water...sorry...
As long as it says 100% silicone and is the clear kind, you can use it. I've built a lot of aquariums. Even if the label says "Not for aquariums or underwater use", it's still alright if it's 100% and clear. The companies just put that disclaimer on there because they were getting too many yucksters that didn't know a thing about building aquariums calling them and wanting retribution for a hundred gallons of water ruining their hardwood floors after a seam gave way. But it wasn't the silicone, it's amateurs trying to built big tanks and doing it wrong.
makaay4 years ago
It's beautiful
nicing4 years ago
Great work and great instructable
Look forward to trying this myself
Absolutely amazing. I had been considering doing something like this for an in-wall aquarium I'm looking at, but all the instructionals I found on the net involved gluing a couple of sheets together (for extra thickness) and then carving them.
Your method lets me keep the overall thickness down to a minimum while letting me have pieces of all sizes jut out. Awesome!
Rainh2o (author)  David Catriel4 years ago
thanks...Yep, to make a ledge just cut the foam the size and shape you want and glue it on edge wise...I tried to use the factory cut edge as the edge to glue to the foam back board, that way it was nice and flat, it will still be thin but will jut out as you can see from the photos.
One worry I have about wide ledges sticking out - the more surface they expose, the more pressure you'll get on the joint because it's trying even harder to float up.
Instead of gluing it flat on the backing, I would carve out a diagonal notch in the backing (i.e. diagonal pointing down) and then fit the ledge into that notch. when the ledge tries to float up, you'll have the extra strength provided by the slot. Sort of like a wide mortice and tenon.
Rainh2o (author)  David Catriel4 years ago
that might work better. I am not too worried about it because the concrete overlay reenforced the joint. But that is a good idea to notch it!
Looks great. Shame I redid my aquarium just last week and will not get to it again for a few months. Would be great to have this tutorial a week ago.
Great work, Thanks.
Rainh2o (author)  TinkerWorkshop4 years ago
You could take the dimensions and then make the background before you redo your tank again, this way it will be ready. Although the fill and drain to get rid of leaching might slow you down, so hopefully you can store your fishies somewhere...
Otterkins24 years ago
Forget the lid instructable and do a base instructable first! I have a 50 gal. tank but nothing to put it on. I've been looking for several years for something inexpensive but attractive to put it on, but so far no luck. Great ible! I can see myself using this technique for armour and figure dioramas. A low stone wall with troops and Panzers rolling past would look awesome!!!
Rainh2o (author)  Otterkins24 years ago
That would be cool!. The stand came with my tank, it wasnt exactly right and I did reinforce it a bit and then I cut the door in the front. there is a lot of info out on the web about building a stand. Basically a couple of rectangles put together with either a couple of upright 2x4's or four 4x4 as uprights and then some bracing crosswise and coverd in Oak or your choice of wood. mine is home built covered in Oak plywood and then stained.
dissidence4 years ago
i hope people use aquarium rated silicone you cant just use any silicone,
Rainh2o (author)  dissidence4 years ago
ilicone such as GE silicone 1 is good. Must be 100% silicone, no mold inhibitors or mildew resistance and it must be silicone and not caulk. I used red devil architectural grade 100% silicone. It has nothing in it that can kill the fish once its cured.
burnnfly4 years ago
Nice job.

If you really want to get a cool effect, get a silicone molding compound --(TAP Plastics has it)-- and make a "texture mold" of a rock; then make your last coat of cement the consistency of bread dough, and press the mold all over it, giving it the same texture as the rocks from which you made the mold.
AZsid4 years ago
Wow. My next tank is getting this. If this guy from Craigslist ever gets back to me I'll have a 50Gal corner tank and I already have an old soldering gun like that looking for a purpose in life. I think some Ghost Shrimp and Diving Frogs would LOVE this thing.
Rainh2o (author)  AZsid4 years ago
I should have put this in the instructible but if your cutting several "rocks" at once, or a big one, you have to go slow and sometimes stop to let the thing reheat. I also used a large rubber band to hold the trigger down and let it sit like that in between gluing and cutting, it didnt seem to overload or burn it up.
evaluna4 years ago
Wow, It's beautiful. Thanks for the great tips and the time you put into this
Absolutely lovely!
5 stars!
szklanki4 years ago
really looks nice
That is very cool. Beautiful job, nice instructable.

I would suggest sealing the concrete. Most concrete has chemicals that kill fish, not just the PH. There is also faux rock spray paint you could use. With a few different colors you could get a pretty good effect. Yours is probably more realistic.
Rainh2o (author)  mr.incredible4 years ago
You may be right, the only thing ultra tex has in it according to the bag is Portland and sand.
21GeeOff214 years ago
so cool. i wish we still had a bunch of fish and a large aquarium to do this in...
Rainh2o (author)  21GeeOff214 years ago
You can do this with any size aquarium, just scale it down. If you had a 1 gal you could use some VERY thin foam to do this with, like 1/4 inch packing foam to make it look right.
yeah... we, unfortunately, no longer have any fish. but this is still cool and i will definitely try it if i get the chance anytime in the near future