"RubenD" wrote in message et...
Using Caleurpa Algae in the tank to remove nitrates would
be a good idea, or it will spread all over as a pest?

Do not use Caulerpa, use Cheatomorpha.
http://www.melevsreef.com/fuge_bulb.html

Anyways, my water condition are excellent (zero Nitrates)
but still get those algae (red hair or green) blooming.

In other words: BECAUSE hair algae is eating all
the nitrates you measure them very low in the water... :-)