Brown and green algae

[Edmontonpup]

The tank was brand new mid November 2011, so the light is 4months old. Just had the water tested at the store and the nitrates,nitrites, ph, ammonia, calcium, etc are all at appropriate levels. Alkalinity is high and Magnesium is low. Just started treating with Magnesium by Kent Marine. Will treat daily for the week and watch for change or a slow down at least. Water testing is done with a strip test kit.

I have 28lbs of live rock, 2 clowns, 3 damsels, 4-5 hermit crabs and 2 small coral frags. Never had fish loss since beginning the tank 2 years ago. The algae issue didn't start until the new tank was started up in November.

When I moved to the new tank, I didn't transfer the sand. So all the gunge stayed in the old tank. We drained the water, then moved the rock to the new tank then refilled new tank with old water.

I do not run a GFO yet.

Any extra help would be greatly appreciated as I am newer to this kind of tank.