Hose clamp

[lastlight]

I was going to suggest wrapping a piece of thin rubber material around it and then securing top and bottom with zipties but for submerged water might still get in there.

I previously used a laguna pond pump and needed to use a gear clamp which rusted too. Not sure what I would have done if it was submerged sorry. You can get larger plastic clamps off BRS I think but I didn't trust one against 3000 gph.

[Kevotron]

Is the band that is rusting, and i couldnt get the part number
plastic would be great but i dnt know where i would find it.
just worried the rust would leach into the water and commit murder on my corals/fish

[gregzz4]

It's odd that the band is rusting but not the screw. It's usually the other way around with mixed-metal gear clamps where the screw is steel and the band is stainless
It's possible the clamp you have is knock-off garbage
If you'd like to try a full stainless clamp, look for a Tridon with the part # starting with HAS ( HS has a steel screw, HAS is full stainless )
If you're having trouble finding one, try a boat repair shop. You can get AWAB, Trident and Tridon to name a few
AWAB are about the best
As for plastic, I can't think of any I'd trust for a return pump
As for rust in your tank, others have stated not to worry about it as it's just iron

[Proteus]

I use plastic ones. They work fine but I don't think they have as good holding power

[jagermaier]

Most hoses fit so tight that a clamp isn't necessary, take the clamp off and see if it holds without it. Stand back in case it doesn't!!

[lastlight]

Another trick I've used is to use a pair of zipties (around the hose and pump) then another two ties to pull pipe and pump together.