I currently have a 20 g tank set up with 1 bluegill and 1 golden shiner in it. The Bluegill I have had for roughly 9 months and the shiner for 4 months (for the 5 months before I got the shiner the bluegill had the tank to himself). They have been fine for the last 3 months but about a week ago I turned on the light to see that the golden shiner was floating at the surface with bits of its skin/mucus coat missing and frayed fins. I thought she was dead until I tried to scoop her into a cup and she swam away. after that she just swam around, ate food and was acting fine it was weird. I did a cautionary water change and left the light on for a full day or so then turned the light off. the next day I turn it on, and again she is floating at the surface and again she does the same thing, although this time her wounds look even deeper. I don't know what to think of it. I took out this plant that was growing this weird algae on it right after the first time she was floating at the surface. it was growing in a thick clump and tore off in a long clump and currently a big strand of it hangs out of the filter output. I first noticed it on a piece of driftwood. anyways, the bluegill is a-ok nothing has changed about him and he looks same as usual. anyone got any ideas?