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.