The tank is about 2 months old or so. The only new fish are the redtail sharks, but I have had them for about 2 weeks now. I have 3 tiger barbs, 2 silver tip sharks, 3 red tail sharks, one black molly, 1 fancy guppy, and 2 orange platies. I don't think anything got in there because the lids are shut. I did a water change on saturday. Other than that I have no idea.