The curious case of the missing fish
I have a 55 litre aquarium with about 6 or 7 kg of live rock which has cycled. It currently has a blue legged hermit crab, a snail and a few coral frags. Yesterday I added my first fish to this tank, a small Randalls shrimp goby which was about 1 and a half inches long. I introduced it the same way I have done before with my other tank, at first the fish was completely fine and was acting the same way it had been at the shop. Later on when I was just about to go to bed I looked in my tank to try and find my fish, it was hanging about at the top of the tank near the water inlet, it was breathing and I thought nothing of it. When I woke up I looked in the tank and couldnt find him, for about 2 hours I looked for him, in the end I took all the rock out to try and find him but he wasnt there. I would like to point out that the tank has a tight fitting lid so he couldnt jump out anywhere and there were no chunks of fish flesh or anything floating round the tank. I spoke to the aquatics centre today and they said that in larger systems with lots of live rock it is possible for a fish to break down overnight but as my tank isnt very large that would happen. Has anybody got any ideas on what could have happened?