Is green algae in a fish tank good or bad?

If the green algae in a fish tank is not too abundant, it indicates good water quality, which is a good thing. A moderate amount of algae releases oxygen under light, and some small fish like to eat it, so algae can be part of the tank’s ecological cycle.

However, if there is too much green algae, it will consume the oxygen and other nutrients in the water and encroach on the fish’s living space, which threatens the fish’s growth. When algae become too plentiful, be sure to clean out a portion in time.