pH Effects on Koi

The pond. pH and its effects on our gorgeous fish.

Over the last decade I have investigated the Koi keepers nightmares, the water quality of Irish water and its effect on my prize Koi. Having fallen into the trap of ulcer disease I have successfully eradicated it from my pond. This will probably be the greatest achievement in my life as I fell upon the solution quite by accident.

Having lived in Ireland for the latter years of my life I extended my hobby from England to here in quite a substantial manner. I now sell Koi to people and help them maintain their ponds when required to do so. I have used my forty years of fish keeping helping others to help themselves in their environment and I still maintain my love of the subject without adding the sales technique that I have acquired as well.

I maintain being a good Koi keeper is deriving the information from books – the writings of better men than me and combining them with the knowledge I have gained over the period to become somewhat of an expert on the matter.

Now water quality has been one of my first defenses in the keeping of ornamental Koi. You can regularly see me first thing in the morning and last thing at night out with the test kits and ensuring that any deviance from the normal is taken care of. Having read that the prime killers in fish are ammonia and nitrite, steps have always been taken to neutralize them from the water if they occurred. Mostly they have never appeared unless an almost complete water change was done which killed off the filter and a complete re-cycling had to take place.

At the beginning of the year three and a half years ago I noticed a Koi which had a bit of mouth rot, as part of his mouth was eaten away. So I caught him and swabbed him and put it under the microscope and noticed that flexibacter and saprogenia were both present in the infection. I chose a standard pond treatment to eradicate the problem and it seemed to work quite well. About six weeks later a dead Koi popped up to the surface and about its body were ulcers and they affected the fish underneath so even if I had seen him before I couldn’t tell that they were ill. So in my panic I bought in the big guns with an antibacterial treatment from Interpet. Again the disease went into remission and I had no more problems for about three months until one after the other I started getting ulcers that you could see and fish that inevitably were dying. After another two treatments with antibacterial products from other suppliers I sat down and almost admitted defeat. Forty years of knowledge went absolutely nowhere in finding a solution to the problem.

I decided that a complete water change was the answer and couldn’t do any more harm as they were all dying anyway. So I changed the water and introduced salt as a buffer to compensate for peaks in the ammonia and nitrate cycle. I researched the salt and found that a 6% dip was the answer to the ulcers spreading further plus a 3% solution in the complete pond. This held the disease in check and it was very traumatic catching the fish, bagging and dipping them every two or three days but eventually I decided that this was not getting me any further with the solution.

I paid a visit to my father back in England and all the Koi I had left with him when I moved here were alive and well and had not experienced any problems whatsoever. So I decided that if the water quality over there was different to here I could help to solve the problem. Dutifully I filled two lemonade bottles from the water and took them back with me for testing.

The results were almost identical except that the pH was different by 0.3% – mine was 8.5 and his was 8.2. In both cases nitrate was non-existent as I had always maintained an eco system was best in any pond and both were well planted with the effect of zero nitrate.

I then turned back to my research notes from when I started the pond and I noticed that in all the records that I kept had only a slight variation in pH when cycling the filters at the beginning of each year and for some reason the pH had risen afterwards by the 0.3%. So I tested the pH four times a day and noted all the temperatures as well. I decided to investigate the pH syndrome to see if that had any answers. I discovered the following information from a website relating to carbon dioxide/bicarbonate/carbonate buffering system (a hold down for pH variation).

I introduced calcium carbonate into the pond gradually over a period of three weeks and together with the salt baths the ulcerations cleared up and the fish gradually recovered and re-grew skin where the ulcers were. I had succeeded to eradicate the problem from the pond, but now, when testing I also test for salt solution and water hardness in the form of calcium carbonate per mg/litre and maintain this as one of my routine chores.

In conclusion I established that the Irish water runs off from granite rocks and very little calcium carbonate is present. Whereas the English water in Sussex runs from chalk rocks with lots of calcium carbonate naturally present in it. This has the effect of reducing pH in the early to late afternoon sun – the technical way of putting it is that the carbonic acid dissociates to form bicarbonate and hydrogen ions. The hydrogen ions produced the acidic forming ions and counteract the high pH and if pH begins to fall then the process is reversed, much the same as in a kettle or a washing machine and a product called Calgon works on the same lines by dissolving the calcium and diluting it back into the water.

I also found out that a block of plaster of Paris about a pound for every 1000 gallons has a similar buffering effect on the water, whereas I thought that plaster had an adverse effect on the water quality and up until then had used a peat to bring down pH.

Just goes to show that no matter how long you are in this game you never stop learning the story, so that’s why I am telling you the tale; you never know it may be the answer to your problems too.

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