Why Is There Fuzz in My Tropical Fish Tanks?

Fuzzy-looking material in tropical fish tanks is from a bacterial bloom or algae growth. Bacteria and algae always grow in fish tanks, but too much of either can deplete the oxygen supply in the water that the fish need.

  1. Types

    • There are many species of algae that grow in tropical fish tanks, but the most common types appear like green or brown fur or long hair-like strands. Bacterial bloom is a sudden cloudy growth of bacteria from rotting food, fish or plants.

    Cause

    • Healthy tank water will normally contain some bacteria and algae cells. When they have access to a large food source and plenty of light, they will suddenly grow in number, according to "Freshwater Aquarium Problem Solver."

    Treatment

    • Do not to overfeed the fish because uneaten food can lead to bacterial bloom. Scrape off algae from the sides of tanks and ornaments and immediately do a partial water change to get up the loose bits.

    Expert Advice

    • "Freshwater Aquarium Problem Solver" states that sometimes a sudden growth of green algae will first appear like white fuzz before turning green.

    Warning

    • "Freshwater Aquariums for Dummies" cautions against putting medications or algae-destroying chemicals in a tropical fish tank because the fish or live plants may be killed.