I have one of these in my 10 gallon. Its about 4 inches long and isn't growing any more. When you first get them, they are very skittish, they will hide whenever you walk into the room. After having 1 for about a year it has finally calmed down and doesn't mind me being in the room with it (but if you stare at it, it will take it as a threat and hide) I think they need lots of rocks to feel comfortable, because once I added lots of rocks to the aquarium was about the time it started to calm down. I found they are very territorial. It will pick a cave, spend all day in it and attack anything that tries to come near (the attack doesn't do any harm, it just shoots out of the cave and bumps into the intruder). Once they settle in, they are very fun fish to watch but it might be a bit frustrating at first when it hides when you try to look at it.