# Attaching a 3D background/filling gaps



## SonicNonsense (Dec 23, 2010)

Hi all, 

I've recently upgraded to a 450 litre aquarium from 200.

I decided to make myself a 3D background while I was at it, so I bought all the necessary polystyrene, and not wanting to use concrete for leaching reasons, I invested in some epoxy based pond lining paint to cover it. Now, it came out really nicely and I'm very pleased with it, but I do have one problem:

I stuck it to the glass with blobs of aquarium sealant, which has worked perfectly on one half of it, but the other half broke free in a couple of places (the polystyrene came free of the sealant, which is still attached to the glass). I assume it's down to the buoyancy of the poly as it's not being weighed down by concrete. This has caused it to come away from the glass partially at one side and at the bottom, so some fish (my fire eel included) have moved in behind it. There's room for them, and I'm not worried for their health behind there, but I never see them! 

I was wondering if anyone knows of anything I could use to plug the gaps around the edge? I can put more poly in underneath to seal up the bottom gap (putting substrate in there is not an option as the eel will burrow into it and potentially get stuck). 

I was thinking of Milliput, but I've heard it's not a good idea to use it in large amounts? I would need to use quite a bit as I wouldn't be able to do it in stages as I wouldn't want to trap the little guys back there. 

Ideally, I want some sort of aqua-safe expanding foam, but I imagine something like that wouldn't exist...

Cheers!
J
:fish10:


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## Big Dog (May 17, 2010)

Try using aquarium safe silicon


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## SonicNonsense (Dec 23, 2010)

Cheers. 

Not sure aquarium silicon will work under water, though, i.e. I won't be able to apply it with the tank still full...


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