Using polyurethane foam on silicone

[numpty]

The silicone isn't really necessary, the foam will adhere to the glass on it's own, but it can help as far as keeping moisture out from behind the foam. You can also just make the perch outside of the tank using the foam, then siliconing the completed assembly in. Or add earth magnets to it with matching ones on the outside to hold it.

Thanks for the reply! I guess I'll just squirt a big blob of foam outside the tank, then finish it and stick it back in later.

Any ideas why the foam wasn't adhering to the cured silicone though? I'm just curious as to whether there's something fishy about either the silicone or PU foam. It was acetoxy cure silicone, if that makes any difference.

Thanks again.