Well! Thanks for the compliment but Im not even close to a "discus guru" just passing on information that I read somewhere.
"airation for a 55 gal discus tank"
Well, that will depend on a number of things like fishload, real plants, filter, etc. Right now in my 90G, I did not have any airstones whatsoever. My setup is a canister filter and no surface movement, C02 injection. Thats pretty much it. Like I said before, no surface movement at all because of the C02 injection. My fishload consists of 5 discus, 1 ram, 11 cardinals, 5 rasboras, 1 honey gourami, 2 otos, 1 sae and millions of snails *crazysmiley* In my opinion, try without and see for yourself. In my experience, airstones are hardly neccessary in a planted tank and besides, aeration just causes surface movement that dissapates C02. The plants surely provide the neccessary O2 requirements.
However, in the non planted tank, I have some surface movement usually from the filter output itself. What Im getting at is that you dont need some fancy aeration system, just your filter output.
Any more questions, feel free to ask. *thumbsupsmiley*