Swollen/red gills

Hi, I have a batch of young blue rams almost ready for sale and quite a few of them have developed swollen and red gills. I have less than 10 nitrates, and have never had ammonia/nitrites. Also, I do 50% water changes every 2-3 days, there are about 55 of them in a 50g tank...

They are eating and swimming just fine, they exhibit no other symptoms, water is 86 and heavily filtered. I also added a bubble wand to really get the o2 in there.

Any ideas? I am stumped. I pulled out one dead body today, the first in many months. Don't know if I should just wait and watch, or treat with an antibiotic. (If so, which one?!) If you have any advice I'd sure appreciate it!

Cathy

I should have added this when I posted...

There has been no flashing, itching, scratching, etc. This is in a fry grow out tank and the only fish added were a few ottos. (Yep, I did QT these guys 1 month before I added them, and the rams' gills were swollen before I added the ottos.) I didn't add plants, gravel, etc. and I keep the temps at 86... I don't think it is ich... the gills have been swollen for a couple of weeks now and there haven't been any white spots... The tank was also treated in the past for gill flukes, I don't think it is flukes either as they are not itchy,scratchy and not showing any evidence of oxygen deprivation.

Thanks for the idea though.

Cathy

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