Platys at top

[fishywishywowoo]

I have 8 platys. They randomly keep at the top of the tank. They aren't gasping or anything,, just hovering at the top of the water. Ammonia 0, nitrite 0, nitrate 10-20. Don't numerous pwc every few days to check wasn't an oxygen issue but it makes no difference. Temp stable. They swim down for a bit then go back up? Any ideas?

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[RedDevil83]

How's the oxygen level of the tank

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[fishywishywowoo]

Not sure. Should be OK. All other fish are fine. Live plants and plenty of surface agitation. Weekly pwc

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