JustNU
Green algae will often begin to grow on base rocks in our saltwater tanks. This is nothing to be too alarmed about in my opinion. If it's bright green, short and attached firmly to the rocks, most likely it can be beneficial to your tank.
If it appears as long hairy strands, it may become more of a problem.
It may continue to grow, or it may fade away.
Snails, hermits and other clean up crew critters may munch on it as well.
But if you like it, and it's growing in a somewhat controlled pace, not becoming a nuisance, then in my opinion - I'd let it grow.
Trying to control every lifeform that shows up in a marine tank by killing it or removing it - sometimes eliminates the diversity that leads to a healthy natural balanced tank.
The tank does not have to look sterile and totally clean to be a good looking tank.
If you like it, and it's not becoming a problem - let it grow.
Green algae does not need to be eliminated.
Green hair algae on the other hand - can get out of control.
The key is to determine what kind of algae it is - before trying to control it.