How to seal a hole in an aquarium?

[Shaolin]

I have recently acquired a fish tank of approx. 200L. One corner has a circular hole about 2" in diameter that had a pipe going out from it. I want to seal this hole. I have some 3mm acrylic sheet and some aquarium-friendly silicone sealant, so questions:

1 - Is the acrylic ok to use? Should I be using thicker stuff?
2 - Do I use the silicone like an adhesive between the acrylic and surrounding glass or place a square onto the glass and just seal around the edges?

[martin_b]

My advice is don't do either!

I'm guessing the hole is for pipework for a sump, something that may prove very useful in the future.

Id suggest a better idea is a trip to the local plumbers merchant and buy the correct sized union and blanking plug, then hide it with a plant. I feel happier from a watertight perceptive with this than glue and acrylic plus if you fitted a tap instead of a plug you have an easy way for water changes with out messing about with a siphon

[Jasandjules]

Shaolin said:

I have recently acquired a fish tank of approx. 200L. One corner has a circular hole about 2" in diameter that had a pipe going out from it. I want to seal this hole. I have some 3mm acrylic sheet and some aquarium-friendly silicone sealant, so questions:

1 - Is the acrylic ok to use? Should I be using thicker stuff?
2 - Do I use the silicone like an adhesive between the acrylic and surrounding glass or place a square onto the glass and just seal around the edges?

Why not use it to set up a sump?

[Shaolin]

Thanks for your replies, a sump isn't possible due to positioning, neither is having anything sticking out from the underside, I want the bottom to be flat. If I seal as I suggested, I could easily cut it out in the future if I wanted to, no?

[Jasandjules]

Shaolin said:

Thanks for your replies, a sump isn't possible due to positioning, neither is having anything sticking out from the underside, I want the bottom to be flat. If I seal as I suggested, I could easily cut it out in the future if I wanted to, no?

I've sealed a crack in the floor of a tank with acrylic and silicone sealant if that helps you.

[lufbramatt]

Don't use plastic, silicone doesn't stick too well to Perspex/acrylic, get a square of glass the same thickness as the glass of the tank cut to cover the hole and use aquarium-safe silicone to stick it down.