i havent kept green severums but i have kept angels. they can get pretty terretorial in small tanks... what ive read tells me that severums are pretty peacefull and will do well with angels.
the tank is a 55g with 3 angles 2 dwarf powderblues, 3 diamond tetras, 3 precox rainbows. Then wife unknowingly bought 3 juvy severums from lfs
She loves the sevs so now I'm thinking of taking largest sev back to store and having 2 sevs, 2-3 angles and a syno. eup. in 55g then get a 29 or 40g for 1 angle, dwarfs, tetras, and rainbows
tank specs:
40w light with moonlights
eheim ecco 2236
aquaclear 300 (hob) used when chemical filtration needed
2 30 aquaclear powerheads for UG filter
several angels and several severums in a 55? I would not. severums turn into "big" (everything is relative) fish. I would not keep 3 adult severums in a 55 by themselves.
A pair of sevs in a 55 would be fine, but not with all that other stuff. Especially if you get a breeding pair. When they spawn they will beat the crap out of anything else in the tank.
angels also get relatively large and if you get a spawning pair they will get territorial and aggressive.
removing one may help with the load calculate 10 gal per angel.
sevs are capable of up to 10" but ..
the min size tank is a 55 for a pair..
I think you may be close to max with the sev and the angels in thre same tank
watch for aggressive behavior. you may be fine with the mix as with all cichlids they can vary in behavior