Hi, I got my 3 Axies last weekend from a very well reputed Aquarium..however they did keep their Axies on gravel as opposed to sand. the small 3 mm gravel. One is doing fabulous! he's the life of the party always swimming and eating . One is a bit sluggish but has eaten 3 times in the week. But my 3rd which is the biggest, approx 1.5 inches bigger than the others ate once last Sunday and hasn't eaten since then. It hardly moves and just hides in his cave. My water tests all say they are in the safe levels. Water 16 degrees centigrade. ph 7.4. Could it be Impacted from the gravel at the aquarium? How do I know? It's a bit hard to tell if it's belly is to big because it's bigger overall in comparison to the others. It just looks solidly built to me. How long until I should panic about it not eating? Confused and concerned