In message , Sue & Bob Hobden
writes
Frogs can and often do bring disease into garden ponds by moving from
infected places. Red Leg is a serious and common disease of frogs that
is transmitted to fish causing serious problems. Every spring I treat
my pond with a suitable anti-parasite/bacteria and the fish (and
arriving frogs) stay healthy.

We did find a fish with a fungal disease earlier this year - we removed
it, treated it but it died. I then treated the pond with FC+.

I also bought a water testing kit - I'll test the pond later today.

--
dave @ stejonda