okay, as far as feeding: I feed good quality high protein foods like Wardley's shrimp pellets, Tetra cichlid sticks and Tetra colour bits (helps bring out the orange/yellow). I feed 5-6 days a week. a day off is good for water quality and digestion IMO. When feeding high protein foods, giving a day or two off each week is good, and your fish will grow as if they never missed a day.
water changes - 1/3 once per week.
The dimensions on the 90 are standard: 48Lx 18Wx24Tall.
its barely wide enough, tall enough, but it is not long enough...
the tank mates are (were- had to move some around to some other tanks):
synodontis eupterus and synodontis notatus (cats)
Pink tailed Chalceus
and
Red Head Severum.
Hope this helps!