I have no idea what happened, except for the water level and pulling the glass back a little. I had the filter over a year. I can only assume with all the factors, I caused the problem. As I stated, I LOVED the filter. You can always give your opinion to me, you can say I am wrong or right. We are only giving opinions to find the remedy, learn and keep striving to keep the fish alive and very happy. I guarantee that if everyone here truly told the dumb and purely accidental things they did from their first tank to now, would be mind blowing. Thanks for responding