I really need help. (Hopefully with a Herbie style drain)

[Snappy]

Add an extension piece onto the return pipe going into the sump so it extends 6-8 inches below the water surface. That way there is no "waterfall" noise.

[Marlin65]

Originally Posted by Snappy

Add an extension piece onto the return pipe going into the sump so it extends 6-8 inches below the water surface. That way there is no "waterfall" noise.

That never worked for me but then I don't have a dorso.
I do think the air into the top is the key.

I think Matt has the right idea,