I didn't see a sub category for this breed so my apologies if there is one. I have a 40 gallon breeder tank with two goldfish, six white cloud mountain minnows and one mystery snail. I have had the minnows and snail for six weeks. I had another snail who unfortunately died last week, not 100% sure why but I assume it was because my goldfish are jerks and eat all of the food and badger the snails which I knew might happen. I've noticed the minnows have been congregating on the bottom of the tank a lot in the last few days. My research across the board said that they tended toward the top of the tank more often than not which was the case until the last few days. I was wondering if anyone had any suggestions for this sudden behavior. The filter speed is set pretty low because if it's too high I can tell it effects all of the fish so that shouldn't be it. The filter is due to be cleaned but it isn't filthy by any means. I've done small water changes every other day for the last week to clear up some cloudiness issues but the levels are good. Please let me know if there are other variables that might help answer this.