I have a 75 gal cold water tank with BIG goldfish in residence, plus 4 catfish and a Plecostomus. The bottom feeders really love these rounds, as they sink - and right now, are too large to be swallowed whole by those piggy goldfish (unless I break wafers into pieces, which they adore). My Mystery Snail also enjoys these - usually Gary finds the wafer before Notch the Pleco does, so Gary gets the first nibbles before Notch wakes up and bulldozes Gary out of the way, to pick up the wafer and go hide in his hidey hole and gobble the rest. Haven't had any trouble with leftovers (goldfish are voracious eaters, and never leave leftovers uneaten) affecting water quality. Tank inhabitants give this I have a 75 gal cold water tank with BIG goldfish in residence, plus 4 catfish and a Plecostomus. The bottom feeders really love these rounds, as they sink - and right now, are too large to be swallowed whole by those piggy goldfish (unless I break wafers into pieces, which they adore). My Mystery Snail also enjoys these - usually Gary finds the wafer before Notch the Pleco does, so Gary gets the first nibbles before Notch wakes up and bulldozes Gary out of the way, to pick up the wafer and go hide in his hidey hole and gobble the rest. Haven't had any trouble with leftovers (goldfish are voracious eaters, and never leave leftovers uneaten) affecting water quality. Tank inhabitants give this 5 stars for tastiness. … more