3D Rock background

[fishgirl53]

Hi Has anyone made a 3d rock background for their tank if so what safe materials were used thank you

[Shilo]

I did one not long ago.  Used some polystyrene sheet from the hardware store which I carved "boulder" shapes using an osculating multi-tool and a small rasp.  To build up the boulders thicker then the sheet just cut excess poly to shape then glue in place with a hot glue gun.  Use tooth picks to put them in place before glueing to test that things look right. Once the shape has been defined either sand it (120 grit) or use a hot air gun or both to clean it up. If you make a mistake just cut off the offending bit and stick on another piece of poly in its place.

I then coated mine with cheap tile grout which worked well for a month until the tanks PH level started to sky rocket.   Normally this happens as soon as water is added then reduces over a few weeks but I removed mine and coated the grout with epoxy.  While the epoxy was still wet I poured sand (black beach sand on the humps and pool sand in the hollows) on it to make it more natural looking.  Been great so far.

Things to think about when making one:

 Avoid any straight lines, there are very few in streams, lakes, etc and they look out of place as I found out with the first attempt when I made too many straight lines in error.  What I was going to do and should have done is to take a photo of a water worn rock face or bank and draw it on to the polystyrene before carving.

Polystyrene floats so you will either have to jam in between the tank bottom and top braces or silicon it to the back glass.  Depending on your tank you may also have to cut it into 1/2 or 1/3rds to get it in.  Make the cuts flow in the hollows like a jigsaw so the joins are not noticeable. 

When designing it use the opportunity to carve the back to hide any returns and other plumbing.

Lastly: Carving polystyrene makes a huge mess. If you do it inside you will be finding polystyrene beads & dust for the next century despite a major clean up afterwards.  If outside then your neighbours will be wondering why it is snowing at summer! 

 

[fishgirl53]

Fantastic I will give it a go your way thank you for the information It will be going in a cichlid tank at the moment I have black substrate in there it is all coming out so am going to be doing a complete revamp on my tank putting in a mixture of silica and coral sand thats on its way now to find another tank at least 100ltrs or more to house my fish for a couple of days till it is all done will post some pic will not be untilafter new year before I start

[Caryl]

I remember someone carving polystyrene with a circle of wire (with a handle tied to it) heated over a gas stove. She then glued gravel to it using aquarium safe silicone. Sand would be better though as it is lighter. Hers weighed a lot, making it harder to position in her tank. Looked great though! The tank bracing stopped the poly from rising.

[Shilo]

I have carved polystyrene with some tungsten carbide wire stretched between a piece of U shaped ply and connected to a 12v power supply.  Worked like the filament in an old fashioned light bulb and cut the poly like a hot knife in butter.  But that was 2 feet long and used for a surf kayak mould, you can get small commercial model making ones of various shapes that would work well on a background.