Tehre are only harlequin and hengeli rasboras in my tank, they are about 2.5cm in length. I went away at the weekend and I'm sure they were all there, the lid is secure and I have checked the floor and behind the tank. I have tested the water and there's no ammonia or nitrites and only 5 nitrates. Theres no skeletons or any sign of the fish, I'm perplexed