The Puffer Forum

Sounds like you've probably got too much livestock in the 20gal which is contributing to the issue.

As far as algae munchers, for diatom (brown algae) control cerith snails seem to be about the best though finding them is often annoyingly difficult.

There's very little goodness in brine shrimp, so best to keep them to an occasional treat. They're kinda like junk food for fish ;) I have a papuan sharp-nose Canthigaster papua myself, so care requirements are essentially identicle to the valentini. Personally I find he loves regular prawns/shrimp ...