Caring for Gymnos is a pretty much the same for all species. I have wild caught Gymnos from all over Uruguay and I keep mine in hard water with a high pH. Others who I have collected with have theirs in slightly acidic pH and soft water so they are very adaptable to whatever water conditions you have. More important is frequent water changes and a winter cool down period. My tanks run in the mid 80s in the summer and get down to the high 50s in the winter. Easiest way to do this is to keep your tank unheated. Ideally you will be able to drop your water temp below the mid 60s for a couple months during the winter. The cool down also prepares them to spawn in the late spring or early summer.
G. labiatus delayed mouth brooders and are sexually dimorphic and males will get to 5-6" while females don't get much bigger than 3-4". They are very easy to tell apart once they are adults but you most likely will not be buying them as full grown adults, females have orange pelvic fins. I'd keep them in a 55g tank with a 2 males and 4+ females. They are sand sifters so I have a sandy substrate and then decorate with driftwood and rock. Hope this helps
