Gymnogeophagus are a fantastic family of fish but they have one major draw back that makes them quite unsuitable for a community tank. They need a cooling period of about 3-4 months a year, this isnt just for breeding its for their health, I looked into these pretty in depth for my tank as they are basically a small geophagus which would mean people with 3-4ft tanks would be able to have them which is something I wanted but when I found out about the cooling I just couldnt have the tank set up properly to keep them.
The way I have seen people keeping them is having them in a show tank at normal tropical temperatures for 9 months of the year but then put them in their own tank for three months and let the temperature match the requirements I cant remember which way round it is but there are northern and southern species and one needs it lower than the other. The temp tank is, depending on species and numbers a long 20g tank.
As with all geos sand substrate is a must.
Have to admit not seen much of these in the shops of any species only seen G.Meridionalis recently. You might have to hunt around for them on specialist forums - I believe there is a geophagus forum somewhere that is based in the UK but cant remember the site name, might be able to find a private breeder.
Just a story to back up the need for cooling period - the store I saw the G.Meridonalis in the owner is a fantastic fish keeper and he had had these in his collection once and his were one of his prize fish for 18 months until one day they all started to die off over the course of a week. I found a lot of other reports of similar things happening to others as well, it really does seem that they change from tropical to coldwater fish very quickly and then just as quick back.
If you can do the cooling period I would go for it, tough to keep but very very amazing fish.
Wills