Well the instructions say "1-2 teaspoons per 100 gallons" per day, which covers a lot of ground.
Until recently, I was dosing about 1/2 teaspon per day in my 30 gallon SPS system. So I was about in the middle, or trying to be. Even with very minimal fish load, tons of flow, and an oversized skimmer, I've had cyano constantly. Not real bad, but constant. So I'll be cutting the dose to about 1/4 tsp per day, which is just under the minimum, per the instructions.
I'd like to raise my nitrates from zero up to 1 or 2, but it seems oyster feast alone may not be the way to do it.
BTW: initially I saw some improvement in the SPS but no more for the last 75% of the bottle.