Not sure what went wrong so fast
Yesterday at feeding time all cories were active and hungry. This morning I had a quick look at the tank when turning the light on and one cory was swimming fast with weird turns up/down then went to the bottom. I was in a hurry as I had an early morning meeting and just said to the kids and my husband this cory was strange. I just came home and one of them, probably the same one is at the bottom breathing heavy, haven't seen them doing that before. And the gills look more redish then usual I will do a 25% water change, but this guy looks like it won't make it The others are fine.
Any idea what may be wrong?