leaping fish

Question
QUESTION: After a long hard winter my pond is now hosting dozens of mating frogs. My fish -- two goldfish, two koi and one shubinkin, all 15-20 cm long -- are gathering at the opposite end of the pond to the frogs, chasing each other round like mad and leaping out of the water.
The pond also contains two adult tench, rarely seen and a lot of 2cm tench fry from last summer.
The pond is 3 metres by 4.5 metres and 1 metre deep in mostly sun but shaded later in the day.
The fountain/filter is temporarily out of action after some creature of the night bit through the cable (it was unplugged at the time).
Last summer I changed the pond liner and did a good clear out of sediment so there are fewer snails around for now.
There is a net against heron but fitted high enough to allow cats and foxes to drink.
The mating frogs have attracted a lot of cat attention.
I have just started feeding the fish again.
I have recently found a few dead tench fry -- i did not expect them all to survive the winter.
Should I worry about my leaping fish or are they just feeling frisky like the frogs?
thankyou, Daphne Liddle.

ANSWER: Dear Daphne,

Thank you for the mail and good to hear that you keep your pond and animals in good shape.
Your request however is somewhat hard to answer.
If the fish are chasing each other it is possible that they are in breeding season.
If the are scared and hiding its more likely they are scared of surrounding risks like birds, foxes and frogs.
If the fish are also flashing it is possible that they have a disease.
In this case I think it is, if temperature is ok, they are tend to breed or if they are hanging at the surface there is not enough oxygen or they have some kind of parasite or illness.

Keep a good eye on them and check the water with some watertests like available by Tetra.
Check especial ammonium, nitrates,...

Good luck and have a lot of "pond"fun!

Kind regards,
Raf
Belgium

---------- FOLLOW-UP ----------

QUESTION: Dear Raf, Thanks very much for your prompt reply. But things have changed rapidly since I sent the question. The frogs have departed almost as suddenly as they came and the big fish are now mooching in the depths again and not very visible.
But I am very worried about the increasing number of dead fry and, on looking at them closley, some of the living fry seem to have a grey bloom about them. I think I will get a pond fungicide and a water test kit. We have a new fountain/uv filter on order.
Your reply was very helpful but I am not sure what you meant by flashing. A few days ago when the big fish were jumping they were twisting as they jumped. I hope this is not a bad sign,
Thanks, Daphne.

Answer
Dear Daphne,

When fish jump often it means in most cases they are having parasites or swimming in water that is from a lesser quality.
Best is to test the water.
Other is to check for parasites, jumping and flashing (flashing is that the fish swim to something and rub to it)is mostly seen when having parasites or poor waterquality.
To check for parasites you need to get someone over that can look with a microscope.

The fry is something different.
Fry is a risky business and often you see them lose life in the next few weeks of birth.
Most breeders tent to set them separate, feed them special food for fry and use products that reduce fungus and microbiological risks.

Hope all go's well and please let us know the water results.

kind regards and good luck,
Raf