Originally Posted by LittleBlueFishlets
So it's always the same tank location that's affected? And this has happened 6 times? (But all the other fish are OK, including the one that's on the other side of the divider.)
Is the divider solid, or mesh?
If it's solid: this could indicate a potential toxin on the side of the affected fish. You may need to clean out this half of the tank, and remove anything that could be causing/leeching toxins.
Yes, it's always the same tank, however, the divider is only a recent addition out of necessity. These symptoms and deaths happened way before the divider(s). It used to be a sorority tank. However, once their numbers were whittled down to three, I separated them. It's a mesh Top Fin divider, luckily thick enough you can't see much more than you could with the DIY solid ones.
I am not placing anymore fish even near that tank until I figure out what is going on. :( If Bessie (the last, remaining girl) passes, I think I'm going to get rid of all the hard decorations, substrate, and thoroughly clean the tank. Just start everything, including the cycle, over.