Glass Catfish

About

Glass catfish (Kryptopterus vitreolus) is the fish that stops people in their tracks at the fish store. Its body is genuinely transparent, with internal organs and a visible spine, rather than merely translucent. Despite decades in the hobby, its true identity wasn't sorted out until 2013, when it was formally described as a distinct species. Before that it was routinely sold and written about under the names of two close relatives, so older literature is often unreliable on this one. In the wild it comes from slow-moving to still, tannin-stained waters in peninsular and southeastern Thailand, which gives you a good sense of the kind of environment it does best in. Behaviorally it is gentle and somewhat timid, which means boisterous or much larger tankmates will stress it out. It is also a tight schooler. Six individuals is really the minimum, and more is better, because a lone glass catfish or a pair will sulk and rarely venture into open water. Small peaceful species from similar habitats make the most sensible companions. One caveat: it may pick off eggs or fry, so it's not ideal in a breeding setup. Breeding in captivity has not been documented.