The following measures should be applied at least 7, better 14 days, very strictly to succeed.
-Measures for the reduction of the nutrients in an area near 0 mg (PO4/NO3)
-Admit no new nutrients like trace elements / amino acids and vitamins (NO B12).
-No water changes, on this occasion, also nutrients are introduced.
-The Silicate concentration in the tank must be absolutely 0 mg / l, check your osmosis.
-Raise the pH factor to 8.4, better 8.5; and hold by addition of Kalkwasser. Besides, the alkalinity should raise, or on relatively high level are held (≤ 12 dkH).
-Reduction of the lighting duration (HQI, MH, T5, T8) to maximum 6h / day (lighting duration of blue light can be longer).
-Everyday suck of the layers for the reduction of the population density and reduction of the toxicity.
-The treatment should be finished in no case too early there; otherwise, a high risk rules the infection once more spreads out. Treatment after the entire removal of all visible layers at minimum 7 more days continue.
Other steps:
Phosphat-Adsorber for the whole period, better consecutively, use (Rowaphos, Contraphos, Elimi-Phos, Timo PhosStop), less feed, Temperature lower.
If the treatment is concluded successfully I recommend a change of the sea salt.
... best of luck.