Mine do very well with New Life Spectrum pellets, Omega One flakes and the occasional frozen brine shrimp, blood worms even beef heart once in a while, they are very good eaters. As far a pH, I personally don't worry, my tap water comes out at 8.0, I would think ideally they would do well with a pH of 7 but I won't fret over it and it would not be a good idea to buffer the water.
Filtration I don't worry much since I do lots of water changes but I would not put anything too strong since they have a high profile.
The biggest issue I've ran into keeping these fish is their aggression towards each other where one can actually kill another which can occur but that is not always the rule.
I think you will enjoy your new adventure with angels.