When I was doing a water change today, one of my danios got sucked through into the bucket. I only use the bucket to dispose of dirty fish water. I put him back in the tank and he seems unharmed. Could he have caught something by being in the dirty bucket? How long before it would show up? I was trying to give the danios away but don't want to expose some one else's tank to anything. I usually put a net over the end of my siphon tube but was in a hurry today. I'll be rinsing my bucket frequently from now on. Live and learn.