Not enough entries. I think some months there were only one or two entries, so it was not a great contest. I think a lot of people, myself included, have a hard time thinking their tank is worthy of tank of the month, because that seems to imply that everything about your tank is awesome. I think the current spotlight contest is more successful because even if someone doesn't think their tank is totally the best, most of us have a favorite fish or coral or some aspect we're really proud of (or not proud of, depending on which contest).