Ive had angels all my life and i honestly have not had any of the agression issues every one is talking about. I had seven in a 55 gal for 6 yrs and they grew from 1" to 4 1/2"to 6" and they had every thing from gouramies to AFBs in with them with no problems. Even when they had eggs . My elaphant nose lived in that tank for 2 yrs and it never had any problem getting food. My other elaphant nose is in with 5 angels , 3 varieties of sharks, 1 firer mouth , severums, tiger barbs, gouramies and a few types of catfish and loaches . It has been in this tank for a yr and is doing fine. Rams and angels do fine together. As far as the AFB as long as you have floating plants it would be an awsome fish in a 75. Ghost knifes are picky and can be hard to look after when they are smaller.