Well something is stressing them. Run all water tests including pH & KH,
perhaps we'll see something. In the meantime, can you quarantine this
particular fish? ~ jan

~Power to the Porg, Flow On!~

ran tests everything ok except pH was 7.8
Unfortunately it looks as if the other two might have it.
There are also 5 small Tench (fingerlings) in there plus another GF.

Peter