Boesmani rainbows grow to around 6", they are peaceful and need to be in groups of 6+, the males are more colourful and show their best colouration when kept with some females to display to.
They require good water quality, obviously no ammonia or nitrItes, as low nitrAtes as possible and its usually best to do 2x weekly water changes. They like a good current in the tank as well.
You can keep them with a variety of other fish, those listed as fine and also can be kept with other species of rainbowfish.
Minimum size tank and this is just my opinion not fact, is a 55g as they do like a good amount of swimming space.
They need a good quality flake food and will also relish some live or frozen food, bloodworm, brineshrimp, daphnia, prawn etc, be careful with pellet foods though as they have a narrow throat and large pellets can get stuck in their thoat as they are feisty eaters.