On Tue, 19 Jan 2010 03:35:04 -0800 (PST), Marge
wrote:

Is standard silicon sealant safe in a fish tank?

I had a problem with waste gathering between a black plastic filter/
pump cage and inside edge of glass so removed the cage and refitted
with standard sealant leaving no gap for water/waste to get between
cage and glass.

Silicon was fully cured before adding water, fish lived happily for
over 6 months but recently had problems and noticed slight oily film
on water suface.

Could this be down to silicon all this time later? could it be
possible that various tank cleaning fluids react with the silicon?

After six months the silicone sealant will not be the problem. The
problems with some sealants is they contain fungicides that kill fish
and some are useless for gluing glass.

Steve

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