What kind of Algae is this?

[Icey MD]

Biocube 32, dry rock, dry sand, 3 mo old. 1 clown, 1 watchman goby, 3 hermits, 2 turbos, 5 astreas, 6 nerites, 3 ceriths, 3 nasserias. no corals.

This green algae popped up over 1 month ago, sometimes looks darker than the picture. never goes away. initially i had a problem with diatoms that came and went, as well as dinos that i fixed with the complete light shutout for 5 days. this algae is mainly on the rock, but also on the glass and can be fairly easily controlled with felt glass cleaning. it doesnt seem to be on the sand. There are some pink specs within the green, which I thought might be pink coralline algae.

ammonia 0, nitrite 0, nitrates 0, phosphates 0, weekly 20% water changes. lights on 4.5 hrs per day +blue lights for 3 hours afterwards.

1) what type of algae is it. green coralline?
2) is it a problem?
3) what should I do about it
4) is it safe to continue adding fish and corals? im concerned that the coral will need more light than i currently have, but if I increase the light, then im concerned the algae will grow out of control.
5) I have a UV sterilizer that I bought when I had the dinos, but never needed to use it - would it be helpful in this situation?

 

[Icey MD]

Also, forgot to mention that this algae cannot be blown off the rock with a turkey baster.