DIY stunning fake internal rockwall - pics and instructions

[Griller]

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Hi guys,

This article is about how I made a large internal artificial rockwall for my 1000L (265gal) Amazon tank.

It makes a great background for fish photography:

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Hopefully I've provided enough info for any monster fish keeper to do the same.

Experimental phase
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Experimental home made artificial rock - Melted styrofoam with rubberized coat sprinkled with river sand.

My 3d internal background was going to simulate a rock wall with plants growing out of the cracks. I started messing around with ideas on how to make it. I made about 15 different fake rocks before I chose my final look.​

Experimental home made artificial rock - Melted styrofoam with rubberized coat sprinkled with quartz crystals - looks like a lamington!

I don't have a picture of all the sketches I made to decide the layout of the tank decor. I think I pumped out 30 sketches before I was satisfied with the look. My final rocks were made from high density styrofoam coated with sandstone bondall pond sealer.

Construction phase

My garage turned artificial rock workshop!

I settled on using high density stryofoam as the background material for the following reasons:

• Non-toxic
• Cheap
• Strong
• Easy to work with
• Insulates the tank
• Acts as padding if the fish hit it
• Lasts forever

Drawbacks:

• Very low density so it doesn't like to stay underwater! It needs serious gluing down!
• Brittle surface can be torn off by fish so it must be coated

Styrofoam rocks being arranged and fitted

What I needed for this job:

• Hacksaw
• Various knives
• Small blowtorch
• Paint brushes
• Silicon gun and aquarium silicon
• A texter
• Sheets and blocks of high density styrofoam
• Dust buster (for the stryofoam bits)
• Drop sheet
• Bondall pond sealer or equivalent
• Imagination

I ordered styrofoam sheets of 3 different thicknesses and 2 large solid blocks for the really big rocks. I cut them up into various shapes. I worked on the big rocks first. Then I rolled the aquarium on its back and put the big rocks into it. I then worked on the smaller rocks to fill the gaps between the big rocks. I only used very thin pieces at the surface because I did not want to reduce the surface area for oxygen exchange.

More foam rocks being arranged and fitted. I wanted to rocks to hide the internal plumbing (recirculation fitting and pipe on the right)

I made the rock shapes by first sketching the shape I wanted onto the foam and then cutting with the saw / knives. I then worked on the detail by cutting with a stanley knife and melting sections with the blow torch. I then hardened the entire surface of each rock by slightly melting it with the torch.

Testing the fit for the plastic plant holders and recirculation jet cover (bottom left)

I carved special recesses into the rocks for the plastic plants to sit in. I wanted the illusion that plants were growing out of the rock wall.

View through the bottom of the tank

View from the side

Almost done

I photographed the positions of the rocks so that I could put them back in their proper place after painting them.

Undercoat applied and then rocks put back to test fit.

I took all the rocks out and painted them with a pond sealer called Bondall. The painting was a very easy process. All I had to do was open the tin and brush the sealer onto the the rocks. Each coat took a day to dry properly. After I applied the undercoat I put the rocks back into the tank. It was like making a jigsaw puzzle ​

Extra rocks (white) being added to fill gaps

As the rocks were painted they became noticeably larger. This meant that they didn't go back into exactly the same positions as originally planned. A few rearrangements were required. I made some extra rocks out of the leftovers to fill gaps and add a bit of depth to the look of the rock wall.​

Final coat applied and rocks placed back for final test fit

After the final coat (3rd coat) I put them all back in again and tested the plants. Then came the hardest part. I had to paint pond sealer on the glass between each rock. I couldn't paint the entire background because the pond sealer doesn't bond to glass well enough to hold the rocks down. The rocks just tear the sealer off the glass when the tank is filled. The rocks must be siliconed directly onto the glass or the system doesn't work! I had to painstakingly trace around each rock and then remove it. Once the rocks were out I painted in the gaps.

Painting pond sealer where the rocks have gaps

I had to paint pond sealer on the glass between each rock. I couldn't paint the entire background because the pond sealer doesn't bond to glass well enough to hold the rocks down. The rocks just tear the sealer off the glass when the tank is filled. The rocks must be siliconed directly onto the glass or the system doesn't work! I had to painstakingly trace around each rock and then remove it. Once the rocks were out I painted in the gaps.

Painting the gaps and the plumbing (the fish eventually pulled the sealer off the pipes)

I then added silicon to the back of each rock and put it in the tank. The painted gaps formed an outline so it was easy to put the rocks in their correct place.

Bottom painted and plants glued in

I then rolled the tank upright and painted the back of the tank black to prevent light shining through the gaps. I added a few rocks to the bottom of the tank and painted the bottom with black pond sealer. Since I planned to have digging fish I didn't want to see exposed glass.​

Wood pile added as a feature and to conceal the recirculation pump

Tank ready to be set up

It was worth the effort!

3 years on:

Algy starting to grow after 3 months

About 1 year in

Artificial rocks looking more natural than ever after 3 years

The artificial rocks are still in very good condition. Algy has given them a distinct brownish green colour and made them look very natural. No guest can tell that the rocks are fake.


List of problems:

• My Oscars nested on a rock and managed to pull off some of the sealer, exposing the foam. I just put another rock over the top.
• There are always annoying fine particles suspended in the water. I suspect that they are detaching from the pond sealer as it slowly breaks down. The particles accumulate in my sump filter and form a kind of glue that clogs everything up. I need to clean it out once every year.
• Most of the artificial plants have deteriorated to the point that they have been removed or replaced.
• I don't think the pond sealer would survive a plecostomos!

Conclusion

I hope you guys enjoyed this article. I'm looking at my rockwall right now and it just never gets old


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[Red Terror_86]

good job buddy! worth it in the end!

 

[MaddMaxx]

very nice end result! how much longer do you think it will hold up?

 

[Pharaoh]

Nice job!

 

[spiff]

Nice! It looks pro!

 

[Griller]

Thanks guys.

very nice end result! how much longer do you think it will hold up?

I think it will last as long as the tank does - 10+ years.

That is what I intended. The sealer bonded VERY well with the styrofoam. It only comes off when bitten through by fish (it took a lot of biting by 2 breeding oscars to get through 3 coats)

Silicon slowly weakens in water and I suspect that the pond sealer is slowly beaking down as well. I have a hunch that the break down is merely from fish repeatedly biting the sealer. I'll know if I see the rocks start coming off the glass. There is no sign of that happening. If it did I would have to re-paint the rocks and silicon them back in

 

[Krawnik]

Very nice!

 

[Matt724]

have you noticed any change in pH since you put the wall in?

 

[john73738]

Great work, cant wait to see it on my wide screen, Pics too big for my work pc.

Bear

 

[jcardona1]

awesome work!