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The algea si most likely a product of the water you are using. It thrives in tanks that have PO4
in them. It is ussually introduced into the tank via the water. The best fix for this is to start using tested RO
water for all water changes and top-offs. RO
water should not contain PO4
. Next time you are at the LFS
pick up a PO4
test kit and see how things are.
With the lighting you described you have 2watts/gal
lighting. This is a bit low to support most any soft corals.