how long for algae to grow

[26y]

My tank has been setup for over 3 months now and I have hydroid larva that need to be taken care of. How long does it take for regular algae to grow so I can get shrimp. My calcium is at just over 400, and I introduced coraline algae but nothing spreads.

 

[ichthyogeek]

Umm, why would you need algae? It seems that you would just need to add the shrimp, which will then graze on the hydroid larvae, right?