Wafers of Algae & Spirulina. AFI Wafers "The Premium Pleco Catfish Tropical Fish Food" Please note: All product photos are not exact, product color and sizes may vary a little These are a Small thinner Algae Wafer Size apx "3/8" - 1/2" in diameter and apx 1/8' thin. These are both sinking and floating for ALL Tropicals, not just Bottom Fish. AFI Smaller/thiner wafers have apx 2000 or more per LB Not guaranteed to Immediatelysink. As with ALL Wafers, there will always be some that take longer to sink. Some may even be Floaters. Our wafers are sifted and graded to remove most dust and most chips