A seaweed aquarium feeder and method allows fish to feed on seaweed food while preventing escape of the food into aquarium water. The feeder includes a base and hinged lid which closes against the base. The lid includes a rectangular recessed seaweed holding windowed area which fits over a protruding rectangular platform of the base. Seaweed food is cut or folded into rectangular sheets captured between the recessed seaweed holding windowed area of the lid and the protruding platform of the base. Windows in the lid allow the fish access to the seaweed food while covering edges of the folded or cut seaweed to prevent tearing off pieces of pieces of the seaweed which may clog an aquarium filter. A magnet pocket in the base holds a first magnet the feeder is held against an aquarium wall by cooperation of the first magnet with a second magnet outside the aquarium.
