Green Spot Algae

This small-rounded aquarium algae sticks strongly in leaves or aquarium glass. They usually appears in new set-up tank or when water quality drops.

In non-planted tanks, usually this aquarium algae will disappear when the water quality recovers or after partially water changes. In planted tanks, this aquarium algae will appear if CO2 level are low. Again CO2 is the key here!, you should keep the CO2 level stable. Since they stick strongly to aquarium plants' leaves, we can't remove them without ruining the leaves. You better cut the invaded leaves to prevent spreading or use algae eaters like Zebra Nerite snail  to eliminate them.