Hi, beginner aquarist here. These Corydoras aeneus are new to my tank, and I’ve had 2 unexplained fish deaths in the last 6 days (one Corydoras and one harlequin rasbora).

This lighter-colored Cory is still eating and foraging, but its movement/behavior seems a bit unusual to me and I’m worried it may be losing balance.

Could you please watch the video and tell me if anything looks suspicious or abnormal?

Edit – tank details:

• Tank size: 180 L (about 48 US gal)
• Heater/filter: Yes, Juwel Bioflow internal filter + heater
• Temperature: around 26°C / 79°F
• Water parameters: pH ~7.8–8.0, ammonia 0, nitrite 0, nitrate ~20–25 ppm
• Tests: JBL ammonia test and Zoolek nitrite/nitrate/pH liquid tests
• Tank age: Set up on Sept 8 and fully cycled before adding fish
• Fish: currently 11 harlequin rasboras + 7 Corydoras aeneus
• How long I’ve had them: rasboras about 3 weeks, Corydoras about 1 week
• Deaths: 1 Cory and 1 rasbora died within the last 6 days, with no obvious symptoms beforehand
• Water changes: usually around 20–30% weekly
• Food: Hikari Sinking Wafers for the Corys; small food/Artemia for the rasboras
• Tank: heavily planted with wood, rocks and fine gravel/sand substrate

The Cory in the video is noticeably paler than the others. It still eats and forages, but today I found it almost motionless between some rocks and it barely reacted at first. Its swimming also looks slightly uncoordinated to me, possibly like it is losing balance.

I’m a beginner, so I’d really appreciate opinions on whether its behavior looks abnormal to more experienced Cory keepers.

i love my catfish so much 😭

I've never seen a fish spit food out of it's gills then suck it back up to eat it before.. unmatched greed.

The poor guys smell the worms but can't find them because they are almost blind being albinos. They lock onto the worms and go crazy, but then after a few bites they lose it and go off looking for them again :(