we feed our fish cucumber, we just chop a small length off, and chop it in half, we bought these special cucumber weighing down things from ebay called screwcumbers (a smooth edged stainless steel coil which weighs the cucumber down). we leave it in till its all gone, it usually only takes a a day and an evening, and all our fish eat it, even the silver sharks! they love it.. i think prefer it to the flake food!