personally speaking from experience, i dont think you have to worry about your bioload yet depending on what other tank inhabitants you have.........if you have a good stable established system with plenty of filtration,rockwork and critters, as well as some coral, i wouldnt worry about that. i am not a big fan of the foxface though! a 90 gallon is a nice size tank.....i have a 75 reef with every coral type and about eight fish......your fine.....i would go with 5 chromis, they reccomend an odd number.....