How Do I Prevent Algae?
Algae will always form in aquariums and is impossible to avoid completely, but unsightly outbreaks can be prevented or controlled with a few simple steps. The most common causes of algae problems are phosphates and nitrates in the water, unsuitable lighting, excess waste, and stagnant substrates:
Phosphates and Nitrates - These pollutants appear in the aquarium from fish waste and from normal biological filtration. With regular water changes and the use of carbon in the filter, nitrates can be kept under control, but you will only know if levels are high if you are carrying out regular water testing. Phosphates can also be removed with carbon but for high levels it is best to use a dedicated phosphate remover.
Unsuitable lighting - Whilst too much light is often blamed for algae problems, it is normally the type of light rather than the brightness. Direct sunlight should be avoided, and if your light tubes are over 12-24 months old it may be worth replacing them. Lights should be on for 10-12 hours a day for planted tanks, but can be reduced for non-planted tanks.
Excess waste - A build-up of debris can encourage algae so make sure your filter is cleaned regularly and you are using a gravel cleaner when doing water changes. Introducing scavenging fish to disturb debris or additional pumps can also help.
Stagnant substrates - Fine substrate like sand can compact, which causes a lack of oxygen and stagnant areas, which often turn black, and this can encourage blue-green 'carpet' type algae. Stir or disturb the substrate regularly, or change to a larger grain substrate
Addressing these issues will help to prevent algae but it will not deal with algae already present. To remove existing algae the best method is to use algae eating species such as some catfish, loaches, or shrimps.