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How to make your own Cliffs

Joseph Huntley

AC Members
Ok guys atm I dont have any pictures but I will soon but thought would explain the process since it is so easy.

I was a taxidermist for many years and we always did fish mounts in natural looking scenes and cliffs and here is one of the tricks we used and I bet It can be used here too.

We also went to the model train store and they have all kinds of really cool rubber molds for casting your own rocks and stuff so look in the train stores too for your aquarium needs.

Step 1: get some scrap plexiglass for a base, also get a couple acrylic rods from local hardware store.

Step 2: Cut your base in the shape you want your cliff wall.

Step 3: drill several holes and cut your acrylic rod to the height you want your cliff and weld them into your base with acrylic or plexi glue.

Step 4: go dumpster diving at your local carpet store for some of their scrap carpet padding. you know the stuff made from chunks of foam rubber glued together to make the padding. (I always ask the store if they are open and they always say no need to hit the dumpster and take me in the back and hand me 20 times more than i ever need.)

Step 5: Cut the width you want your wall plus maybe 1/2 inch wider and do this until you have enough layers to make the height you want.

Step 6: TEAR DO NOT CUT the front of the padding giving you random shapes. your front will be rough like rocks and you want to tear like a wavy pattern to the front so your layers of rocks are all different.

Step 7: Randomly grab your layers and poke them onto the acrylic rods you might want to sharpen the tops of the rods a little to make it easier.

Step 8: once this is all finished you should have a nice stack of foam padding and it will look like a really nice rock faced wall.

Now for the Finishing of your Wall

Finishing 1: Use whatever aquarium concrete you guys use and start out with a thin coat and completely coat the foam front and rear so that the foam is completely encapsulated. we used plaster of paris but in an aquarium I doubt that will work.

I assume you can also use urethane's or plastics for making aquarium stuff (maybe someone smart with aquarium materials for these things can make suggestions.)

Finishing 2: after the initial coat has dried you can start layering a few thicker coats on until you get the desired thickness you want. Also you can use natural sponges while the coating is still wet and dapple it around giving the rock some more texture.

Finishing 3: for your final coat you might want to tint your concrete mixture so that it is a lot easier to paint to your desired color later on.

Finishing 4: add final painting and clear coat as desired. the plexi base is created with a couple feet will be able to be slid under your substrae and even put a couple regular rocks on top to hold youe wall to the ground.

Once I learn more about materials I will make one for my aquarium and update this thread with some pictures of the process


Joseph Huntley

AC Members
ok guys I promised you some pics. this took me less than 5 mins to make and with a little more finesse would make an awesome looking cliff (just like our fearless leader ))

now the only thing I skipped here was the concrete coating but I dont think i really need to show that we all know how to add concrete besides I wasnt abt to buy a 50 lb or whatever bag for this lil thing wouldnt have a use for the rest rofl. I even found some of my old taxidermy pics showing some of the various backgrounds and landscapes I did but their not scanned so cant post

Joseph Huntley

AC Members
ok so here is the scoop I basically covered this earlier but will add a few "Cliff Notes" lol

First toothpicks and bamboo skewers are really handy for using as posts for holding the stack together they work great for your foam rocks too until you are ready to glue them all together.

if you have a spot you want to do a nice overhang remember this is foam rubber so it will go limp I just use a couple bamboo skewers and it holds it night and straight.

I have taken good ole Elmer's glue and thinned it some with water and let the pieces soak in that for a few mins then let them drain and drip for a couple mins then set on plastic to dry. this makes them hard and stiff so when you set them in place they wont droop and you don't need to stiffen with sticks.

So the first step is to rip some pieces and start making your stacks. don't worry if the pieces don't match this is nature and everything is random. be sure to not use just one long piece make several short ones so that you have Little caves.


Joseph Huntley

AC Members
after they are all made and stacked the way you like you can take apart and start to silicone them together.

now the part i don't show is you can now concrete them and since they are foam rubber they will absorb a little more than foam but should be able to stay on bottom of tank on their own weight.

Now after concrete you can use Krylon Fusion Texture Paint and give it its looks and highlight and other fun stuff.

I didnt have any on hand so for demo purposes only used a can of rustoleum texture paint. and for a fast 5 min cliff wall it actually looks pretty convincing and would look really good and natural if I took my time and concreted it and detailed it a little more with highlights etc


Joseph Huntley

AC Members
and there you go guys how to make a cliff using Foam Carpet Backing.

Now I just tore the edges but to get an even more cool look tear tiny pieces off the tops too it will give that rough look of rubble.

Also this took like 5 mins so its not perfect but the idea gets across. after you concrete it you can remove some of the foam from the inside as you wont need it any more. then you could silicone some PVC tubes in place and add a little concrete to the inside then take a dremel tool and cut out the cave openings. and you will have some nice caves for your fish to hide and breed. You can stack this as tall as you want I just did a short base. I been reading up and abt to get some concrete and start one for my 75G and I will post some pics here of the entire start to finish process

but it doesnt take many pics just some imagination to make a decent natural looking cliff wall


Global Moderator
Staff member
Looks awesome Joseph!

Have you tried one in an aquarium environment? I'd be afraid stuff would leach out into the water.


AC Members
I remember reading another cliff building thread where the OP said the cemented pieces had to be cured in water for at least a month before it stopped leaching

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Joseph Huntley

AC Members
thanks guys

Freshy I am going to do one for my aquarium but like said in last post after you create your concrete outer shell and its thick enough I would remove most of the inside foam rubber. you can then put a couple coats of concrete on any remaining inside to seal it then leech your concrete in a tub of water.

Since carpet backing is just foam rubber there shouldn't be anything harmful in that only the concrete leeching.

Another way to do it would be to make narrow 3/4 inch strips of the backing material and glue it to the front of some blue foam then when it dries tear the leading edge to give you the rough look.

I will be playing around later this week trying various variations on the cliffs. the only reason I like the foam carpet backing is when you tear it you get a really natural rock look with little to no effort.

Joseph Huntley

AC Members
while I was out today guys I got some materials to start my cliff background.

I got white beaded foam (6 bucks for 6 sheets 48 x 3/4 x 13.5)

still have some carpet backing and some pvc for pleco caves in my wall

got some great stuff foam

100% Silicone

Still have few pieces of Blue Foam

and will use some 2 Liter Soda bottles for the plastic for making little caves for shrimps and the other fishies.

Plus I have a bunch of other stuff in the work shop I use for my business and all is easily gotten.

I went by Walmart yesterday and they have tons of bottles of non toxic acrylic paint and they have various sizes starting at 56 cents up to abt 2 bucks so there's where you can get your paints.

So I will still have to get my concrete later but for now enough to start.

So this will be a 3D background built with a mishmash of all the various methods ppl describe using to make their backgrounds. This way I can mix and match all the different materials so we can see how they all work together to form a really easy cool background.

that is if everything works out like I think it will.

so going to babysit grand kids in an hour so tomorrow will start the project

Joseph Huntley

AC Members
well I started my background today. so far it is just a stack of 3 beaded styrofoam and a blue foam backboard. I have it siliconed together and am just letting it sit for a while for the silicone to cure.

I took my welding wire brush and stroked the leading edge of the styro and then took my heat gun and ran it over the front of the foam to melt it some. I was actually surprised it really does give a natural rock look to it. I will take pics later.

this is the base of the rocks so i didnt do tons of detail to it as it will mostly be hidden by the substrate.

I also cut some small 3/4 inch PVC tubes and one 2" pvc half tube for little caves and the big one for plecos. I also have some Plexiglass for the bottom of the pleco cave so he doesn't munch on the Styrofoam. I will coat the inside of the pleco pvc with silicone and lay a layer of sand inside it and on the floor so it looks more like a sandy cave. I know I could have just bought some pre-made but like said with Father in law in nursing home we are on a tight budget.

Plus the fact this is so we can see some innovative ways to do the same thing right?

Ok will post more and some pics later as I get rolling