Low mg.

[Myka]

So you're not using GFO or other means to lower PO4? Lots of tanks produce too much PO4 for the carbon dosing to take care of it.

Your clean up crew is pathetic. Start there. For hair algae, I'd add 6-8 Turbo or Trochus Snails and 6-8 Scarlet Hermits.

Once they get to work the PO4 will probably go up because they will be eating and pooping it into the water column. At least your skimmer and the gfo youre ging to add can help at that point. Should solve the problems.