Mark Cable wrote:
If anyone can help me with this I'd be most grateful.

I'm not an experienced ponder but here's a thought.

Could it be that by adding the airstones you've destroyed the normal
stratification of the water (cooler at the bottom, warm at the top)?

Obviously you've had water circulating all the time with your filtration but
now you've changes the way water's moving in your pond. By improving the
mixing you've perhaps robbed the fish of some of their "comfort zones".

Tim

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