Algae Blooms in Freshwater Tanks

Algae is the simplest form of plant life, and it can rapidly take over an aquarium when the conditions are right for growth. Algae spores are not overly particular as to where they grow, and algae blooms often occur even in new aquariums. By understanding what causes algae blooms, you can prevent them or get them under control if they grow in your aquarium.

  1. Causes

    • Keep your fish healthy by ensuring their water is clear and clean.

      Algae blooms are caused by an imbalance in the water chemistry in the aquarium. A balanced aquarium will have some algae growth, but it should be kept under control. Algae blooms occur when the level of dissolved nutrients in the water is high, which are caused by phosphates in the water, fish waste or decaying material such as uneaten food and dead fish.

    Types

    • Not all growth in the aquarium is caused by algae. If the growth is green, red or purple, it is probably caused by other organisms such as diatoms or cyanobacteria. True algae is either single-celled phytoplankton that floats in the water or filamentous and mossy in appearance. Green water is caused by the single-celled type. Filamentous algae sticks to surfaces in the aquarium.

    Prevention

    • Avoid doing large water changes. Water changes remove zooplankton, which feed on phytoplankton. An imbalance can cause sudden blooms in phytoplankton numbers, turning the water green. Use distilled or reverse osmosis water if you live in an area where phosphates are high. Phosphates act as a fertilizer that causes algae to grow. Do not overfeed your fish, and vacuum the bottom of the tank regularly to remove uneaten food. Remove any dead fish as soon as you notice them.

    Treatment

    • Algae is best treated by performing water changes and adding organisms to your aquarium that eat algae as food. Chemical controls may work temporarily, but if the underlying problem is not addressed, the algae bloom will return. Chemical algae controls can also harm invertebrates in the tank. If you notice an algae bloom in progress, do a partial water change to remove phosphates and nutrients from the water. Add algae-eating fish, snails or shrimp to remove filamentous algae. Not all tanks are suitable for all types of algae-eating organisms, so research to ensure that you are adding a suitable organism to your aquarium.