I bought fish 3 days ago.. Just some danios. And i have a few goldfish already in the tank. Everyday since I bought the danios I have been finding dead ones on the intake of my filter. I noticed that at night all the fish go towards the intake since the current of the out on my filter would push them around while they slept. Could the filter be sucking them in as they sleep? I test my water and got it tested at three LFS and it is fine. What is happening!?