Slightly bloated celestial pearl danio that swims by the surface

[qoob]

Found one of my danios in my surface skimmer a few days ago. Modded the skimmer so that fish can't fall in anymore but noticed the same danio kept being sucked in. He was constantly swimming by the surface (I've measured o2 with a drip kit and levels are very high) and so slowly he was caught by the current and kept being sucked in. I netted him in a big net and left him there.

He is slightly bloated from one side (picture). Not interested in food and the peas I tried to feed him. No other symptoms that I can see.

One night after netting he is very lethargic. What is wrong? No other fish has any of these symptoms (9/10 CPDs, 13 ember tetras, 2 honey gourami, ~30 shrimp, 5 otocinclus). One oto wasn't doing so well and had an empty stomach, so I netted him too and added a blanched zucchini slice in there, which he isn't interested in. Fish were added 2 weeks ago.

Ammonia 0, nitrites 0, nitrates 5-10, pH 6.2-6.6 (co2 on/off). Temperature 24.5 Celsius.

 

[qoob]

In 24 hours after netting him he became so lethargic he basically just laid on his side in the net. I tried introducing him back to the tank without the net, but he just sank to the bottom. Other danios immediately started picking at him for some reason. I then decided to euthanize him. I also euthanized the oto that looked like he was going to die a day ago. His tummy was completely caved in and he would not eat anything I offered. Also he was laying on his back/side in the net.

 

[libertybelle]

Sorry you had to euthanize fish; that’s always hard. How long have you had them? If they were relatively new additions (especially the oto) I’d say just keep an eye on the others. Otos in particular are tough to feed sometimes and usually come to you in pretty rough shape. I usually expect to lose a couple when I buy a group.