I bought a used marine land reef ready tank and all the return cutouts have been removed. I’d like to cover those holes. Does anyone know where I can get new ones or a way to cover them up?
I assume you are referring to the punchout in the top of the 'fence' where a return pipe would normally stick through into the tank. I assume the reason is so that water isn't flowing through there.
Easiest might be to put a PVC cap over the hole and then glue it in place.