That greenish glow in your aquarium may fit in with St. Patrick's Day, but what can you do about algae growth the other 364 days of the year?
If algae hasn't taken over the tank, you may not have to do anything. Healthy growth of green algae in an established aquarium will happen naturally and is a sign of good water quality and adequate lighting. However, red or brown algae indicate poor water quality and low-light conditions.
After a tank is running for about a week, you may notice a brownish color beginning to take over on rocks and substrate. Don't worry about this. The brown comes from a growth of diatoms, microscopic plants that require little light and are tolerant of many water conditions. If you have properly conditioned your tank and are providing at least eight to 10 hours of adequate light daily, you'll soon notice that brilliant green algae begin to take hold.
But algae can get out of hand if your tank has too much phosphate or as nitrates built up, receives too much light or lacks herbivores (plant-eating creatures). Microscopic algae that appear as greenish “films” on glass are easily cleaned with a rag or controlled by herbivorous species. Snails are often thrown into a tank to thwart any overgrowth, which usually works well. However, watch out that you don't end up having a snail problem, since many of these species are astoundingly prolific.
You can also help control algae growth other ways: