Koi Carp Acting Strangely..

[-FighterFishh]

I know that this part of the forum is probably aimed at tanks, but I figured that ponds could probably be posted here too.

We have a pond out in our back garden which houses 3 butterfly koi, 2 normal koi, a comet, a shubunkin and a large goldfish. None of the koi are fully grown, but the butterflies are slightly older. The normal koi are still about the size of the shubunkin.
The strange thing is, in the last few days the koi have been acting very strangely, lying on the bottom and looking completely dead. At first we thought it was only one of the butterflies with fungus (which we're treating), but it turns out they're all doing it. I went out there just now, and my butterfly was lying on her side, completely still, and another was next to her on his front. I shook the net on top of the pond (puppy guard!) and they both swam away.
I came back with my test kits, and all the levels are fine. By this time, all the fish in the pond had huddled to the deepest part.
All the fish are eating fine and behaving normal apart from when they're doing this.
The pond is about 1m deep, but in an L shape, so I couldn't say how long, but it's definitely big enough. The filter is fine, too, as it's been running for a few years now with no problems!
My mum seems to think that maybe a frog got into the pond and caused some sort of virus, but I'd like some help so that we can figure out and treat the problem.
Any ideas of what is causing them to do this would be much appreciated.
Thank you!

 

[mark4785]

May I ask what your ammonia, nitrite, nitrate and PH level is?

From experience of keeping a pond for some time, generally, the following things cause behavioural changes:

1. fluctuations in temperature - will make them go off food and go more lethargic on the base of pond.

2. fluctuations in KH and GH - in spring/summer, fish metabolism, uptake of c02 by plants and nitrification (the process by which ammonia is converted into nitrite and then to nitrate) all conspire to lower the KH/GH level of the water. An ideal KH is 6-8 dH. An unideal KH below this level can cause a PH crash. GH is involved with nitrification too, and so if your ammonia and nitrite levels are zero then this is an indication that your GH is at the right level; the correct GH is 7-15dH.

3. An incorrect PH (above 8.4 or below 7.2) - this will cause the fish to rub it's skin on pond objects which may explain why one of your fish has a fungus growth since fungus only grows on or around breaks in the skin/ulcers etc. A KH level of 6-8dH will stabilise PH so that it doesn't crash or fluctuate too much.

4. Sleeping sickness - occurs in Koi that are usually under 2 years of age and which are in very cold conditions. Must be treated immediately by highering water temperature 3-4 degrees C per day.

5. Swimbladder issues - the swimbladder organ in your Koi is responsible for allowing it to maintain it's balance. Fish which look like they are listing from side to side, nose diving, floating at the surface etc will have some degree of swimbladder issue. If there was a bacterial cause for swimbladder in your Koi then it probably would not be able to maintain it's balance enough to be able to eat. As you've said it's still able to consume food, the Koi has probably just gulped in too much air into it's swimbladder which is causing minor problems with balance. They may be gulping air if there is a lack of oxygen in your water; make sure you have plenty of water surface agitiation to rectify this. Feed all of your fish cooked garden peas as this will help to relieve some of the trapped air.


Mark.