I'm in the middle of setting up a 90 gallon tank and want to run some numbers by everyone. It will have 4x65W, 6700k k ighting and well stocked with plants. Pressurized CO2 with an aquamedic 1000. Probably will have discus and other assorted fishies.

So, following EI does 3/4 tsp KNO3, 1/4 tsp of KH2PO4 and 1/4 tsp of K2SO4 every other day and 1/4 tsp of CSM+B, does that sound right?

Flourite as a substrate, cannister filters... thanks.

Yes, but you might reduce the KNO3 when feeding/having a good sized load of large cichlids like discus.

You might only need 1/2- 1/3 teaspoon 3x a week etc of KNO3.
I had a 90 for 10 years with Discus with about 1.5X more light.
So you should be safe with the routine and be able to feed well.

Regards,
Tom Barr