Well, when it comes to missing fish, i dont have a clue. What I mean is I have had a cardinal, cleaner wrasse, and a snowflake eel, all three of these fish are still MIA and that was 3 months ago. I have not a clue what could of happened to these fish, I never found them and probably never will. I dont have anything like an overflow box for them to go in and nothing that could have sucked them up or fish that would have eaten them. But I did have openings in the back of the tank where they could have jumped out and I also have a cat who is quite the fisherman. So about 2 moths ago I I completly sealed off the back of my tank so the fish cant jump out and my cat cant get his paws in their and grab the fish. I have not lost a fish since I've done this, so maybe you should check if you have any openings where the fish could have leaped out of the tank.