Mikrogeophagus ramirezi is not a species I recommend, as you'll know if you read any of my stuff in PFK! It's a difficult species to maintain, and the quality of the fish in the trade is low. The main problem is that this fish must have warm (28-30 C) water that is both soft (5 degrees dH, at most) and quite acidic (around 6 being good). Soft and acidic water isn't what filter bacteria like, and in fact below pH 6 the bacteria may stop working altogether. So water quality is a major problem when running these blackwater tanks, and often people use zeolite instead.
If you are not keeping your
Mikrogeophagus ramirezi in very soft, very acidic, very warm water, then you won't have good odds of long term success. This is why I don't recommend these fish, and personally wouldn't touch them with a bargepole.
Mikrogeophagus altispinosus is altogether a much better fish and the only member of the genus suitable for casual aquarists or community tanks.
Mikrogeophagus ramirezi is for expert fishkeepers only, and cannot be kept in community tanks.
On top of this,
Mikrogeophagus ramirezi needs very low levels of nitrate, and anything above 20 mg/l is likely harmful to them. Farmed specimens are said to be maintained using antimicrobial medications, and that would certainly explain why so many specimens get ill within a few months of purchase: without these medications, they get weaker and less resistant.
The particular infection to watch for is
Hexamita. This protozoan likely infects all farmed cichlids, but only in certain circumstances does it become a problem. Nitrate is a key triggering factor, and you often see
Hexamita-infected cichlids when cichlids are kept in overstocked or otherwise improperly maintained tanks. The first sign is the production of long, pale faeces. Put simply, the protozoans irritate the gut, and the gut produces larger amounts of mucous than normal. This is what the long and pale faeces are all about.
Hexamita protozoans in the gut can be fatal once they expand to the other internal organs, resulting in lethargy and bloating, but usually you see another symptom, "hole in the head", where the protozoans somehow travel to the sensory pores on the head. A combination of these and secondary bacterial infections produces the tell-tale ulcers on the head.
I've
written about Hexamita over on Fish Channel, and discuss the treatment there, so there's no real point going over it again. But suffice it to say that you can't cure
Hexamita without using Metronidazole. General cures, tonic salt, etc. will have no affect at all. In combination with the Metronidazole, you'll also have to optimise living conditions and apparently diet too, because diet (typically a lack of greens) seems to be a major factor in some cases. A lot of aquarists assume their fish eat mostly bloodworms and other small animals, yet in the wild, fish like
Mikrogeophagus ramirezi will be consuming a lot of algae and organic matter, and that may be a key source of vitamins that we don't consider when feeding them meat-based foods.
Cheers, Neale