"Green water blooms are common in new aquariums because of the build up of ammonia and lack of benenficial bacteria. Doubtless, green water has saved many fish rfrom an untimely death due to ammonia build-up by converting it into more algae. When these aldae are finally removed from the aquarium, so too are the nutrients."
Causes of excee algae
" Algae are goig to appear in your tank, and that's all there is to it. Every aquarium has algae in it, at least in small amounts. But there are certain events that can trigger serious problems, or result in overproduction of algae (an event referred to as a "bloom"). For all intents and purposes, algae are plants. Just like any other plant, they do best with a lot of light and a lot of nutrients. If the tank lights aare on too much, you'll get algae blooms. If there are too many nutrients in the water, you'll get algae blooms.
Nutrients can come in many forms. Excess fish food is the most common culprit. With too much fish food, food is left uneaten and remains in the tank. This waste settles and becomes mulm, which eventually becomes alge food. The second most common culprit is the presence of too many fish in the aquarium. In this case, you may never see excess fish food in the tank, but the fish are producing enough waste to fuel algae growth. A low-grade fish food may also result in the fish excreting too much waste. Lastly, your water supply may be high in plant nutrients, such as nitrogenous waste or phosphates.
After the nitrogenous wastes (ammonia, nitrite, nitrate), the most important two nutrients for algae are phosphate and silicate. Phosphate can come from fish foods, certain chemicals (especially to control ph) and particularly tap water. Silicates most often come from tap water."
from Algae Headaches written by Joshua Wiegert in Freshwater and Marine Aquarium
