I never kept them but I was going to get a few so I did some research on them. They are very inactive and are sit and wait predators. They like to burry themselfs in the sand and when prey swims overhead they use their huge mouth to create suction and swallow it. They arent too hard to keep alone, but with other fish there can be a few problems. They do have huge mouths so you have to choose tankmates that cant fit in it. Also they have been know to cause sudden drops in the pH of the water. The Chaca Chaca seems to be able to handle this, but tankmates may not be able to and I have heard of fish being lost because of this. An easy solution to this is frequent water changes and a larger tank as this will lessen the severity of the pH drops.