Almost all the Mikrogeophagus ramirezi dumped into standard community tanks die within months. These fish MUST be kept in very warm conditions, around 28-30 C (82-86 F). Too cold, and their immune system and digestive system don't work properly, and sooner or later you have to deal with things like Hexamita.
Conversely, you cannot keep things like neons, danios or Corydoras this warm. They will hate you for it! Neons and danios prefer fairly cool water, around 22 C (72 F) while Corydoras mostly do best under 25 C (77 F). If they're too warm they will have a shorter lifespan and will be more prone to disease.
Over at Wet Web Media I have to explain these facts once or twice a week. It gets boring very quickly! Have you ever wondered why neons die so easily? Or why people can't keep their ram cichlids alive? Temperature is critically important, and yet too many aquarists don't think about this factor at all. Please spend some time reading about a fish before buying them.
I'll also make the point that Mikrogeophagus means "little earth-eater". These are sand-sifting cichlids. Gravel is not an option! Give these cichlids what they need: a sandy substrate tank with some floating plants for shade, a high temperature, gentle current, 0-20 mg/l (maximum) nitrate, and regular water changes. Super-soft water isn't essential, but it helps, and certainly don't keep them above 10 degrees dH, pH 7.0. Wild fish will be living in water with less than 5 degrees dH and pH 5-6. Don't do these things and they won't live that long. If you must add tankmates, choose fish from similar warm-water conditions, such as cardinals.