If you only have one bottom feeder or if your tank is smaller than 20 gallons, it is recommended that you only use one half of an algae wafer at a time so the uneaten portion of the wafer does not continue to dissolve and make the water in your tank cloudy.f your bottom feeders haven't eaten it within an hour they probably won't-then the wafer will just continue to dissolve and your water may become cloudy as a result. You can also try breaking the algae wafers into smaller pieces and only using a half of a wafer instead of a whole so it is eaten faster.