Most all species temp runs 78-82. Prefer soft water for breeding purposes but many believe they do better where HITH is concerned in a harder water. Large variety of foods prepared and live frozen, shrimp night crawlers krill etc. If at all possible get them off of feeders if you can. Some are very stubborn, I have one. PH isn't real important unless you are trying to breed. 6.5-7 is fine.
As for as how much, the more you feed the faster they grow. They will eat as much as you give them. But do let them fast once or twice a week especially when young. They can have problems with a bloating when around 4 inches or less.
That should give you enough of a start, do research when it comes to individual species.