Mine dig the sand, but I also have some with gravel. I think the most important thing is the water for cons. I absolutely love convict cichs and have always kept them.
I have a female convict in a 20 gallon tall. I have had her for almost a year and she is fine. The only problem is I can not put anything in there with her she harasses tham. I even tried a firemouth and she chase the poor thing every where so the firemouth had to be moved into the 45 gallon tank. I will say one get it young and add any fish you want in with it right away so that it will not get used to being alone.
