Folklore wrote:

On Sat, Mark Swinkels Said:

If the housing is made of ABS or PVC then your best bet is to use the
appropriate solvent cement it will make a stronger and neater repair than
any 'glue' and the solvent will evaporate in a day or so leaving nothing to
harm the fish.

Thanks Mark. I'm not sure if it's ABS or PVC or not. There's no
indication on it anywhere. Given your tip on the PVC solvent evaping
though I think I'll give that a try first.

Failing that, look for an adhesive called "goop" here in the USA. It is
like silicone rubber, but hardens, and sticks to most plastics.

Plumbers Goop will also bond pvc piping.