I purchased a test kit and measured the levels of nitrites, ammonia, phosphate and PH. The levels of nitrites, ammonia and phosphate are zero. PH is high at 9.0. Could this be causing the loss of my fish? Thank you!

Hi Pine Acres. So sorry to hear about the death of your Koi. I've been in the pond hobby 31 years now and in my experience, water conditons could be one of the reasons for the death even though the test kits say that the perimeters are good. Many times test kits give wrong readings because they are old. Also, during the winter the warmest part of the pond is at the bottom and of course this is where the Koi stay, therefore, water testing should be done at the bottom, in my opinion.
If the pond has been around for a while I suspect that there must be a lot of plant debris at the bottom which can decay and cause toxins to be emited. I make water changes from the bottom of my ponds right up until the water starts to freeze. This way I am removing as much of the toxin build up as possible as this is where toxins congregate

I would make a one third water change from the bottom of the pond and see if this stops the fish from dying. Also, a good bio-filter which can be easily made would be a good idea. When we had our 13,000 gallon pond we used a 300 gallon bio-filter to keep our water clear and free of hair algae and to keep our fish healthy.

Your's Koily, Lorraine

I wish I could be of more help but there isn't much to work with. Have you introduced any new fish or plants to the pond that may have brought something with them? Its spring time, have you put any lawn chemicals down that have found their way into the pond? I trust you are not feeding them yet. Do you have all your equipment started up for good water movement and filtration? Are the other fish behaving normally or are some acting sick? If it is sudden and wide spread I would lean toward bad water. Just some things you may or may not have thought of yet.
Good luck,
Mike K

Mike K

I think Lorraine's ideas are good! My pond is a bit bigger than yours and fairly new. I am stuffing as much filtration into my pond as I can. I am even adding plants and medium to the waterfall.
I read that water celery and sweet potato vine work really well as filtration so will be adding those as well.
Sorry I can't answer your koi issue. If koivet is still online, they seem to know lots about fish too.

I also think that regular, frequently 25 to 35% water changes are called for. The water you drain should come from the bottom of your pond. Also, not sure if you have done this but, I would suggest that you get a fresh test kit and retest the water, also frequently. Keep us posted on how things are going. Not sure you have a vet than can or will do it but if you do and you have a deceased fish they can do an autopsy and possibly give you some more info. Of course that may be costly, just don't know. Good luck and hope things get better very soon.

Pine, how are your fish doing?

Lorraine