Bloated Tiger Barb

[fish_luver]

I have a 46 gallon bowfront aquarium and have had it set up for almost 6 months now. I have a variety of freshwater tropical fish and haven't had too many issues. Just today, when I was do my routine water change, I noticed that two of my Tiger Barbs looked bloated. By the time I finished putting fresh water into the tank, one of them was barely even trying to swim anymore, but is still breathing and would spaz out randomly. The other fish seems to be in good spirits but is showing signs of bloating as well. I've had these fish in my tank for 4 months without any issues. I've attached a photo of the worse case for your review. Please help! I put the two suspect fish in QT and put the heat up to 80 degrees and have a lot of air flowing through the water. I don't know the specs of the water b/c I don't have a kit to test it. Any input or suggestions would be appreciated!

 

[fish_luver]

When I woke this morning, the worst one had passed away. The other Tiger Barb was no longer bloated and was swimming around happily, he had just lost some of his color. I'm not sure what happened, but I'm glad it only claimed one fatality instead of two. If anyone has any feedback on what might have caused this I would really appreciate it! Thanks!