Last Friday I decided that the only solution to a daily fluctuating and high PH level (0.3PH variation from 8AM to 5PM) was to cover the pond. So, on Friday night, I rigged up a temporary cover until a more permanent solution could be found.
During my saturday morning maintenance regime, I discovered a sudden and worrying leap of ammonia from a stable zero to 0.5ppm. What on earth was causing this? That was my initial reaction but it dawned on me that the cover has altered the amount of light reaching the pond and consequently, some algae was dying and ammonia was the inevitable result. The next thing I needed to know was just how dangerous the level actually was on a short term basis. I new the filters would compensate, given time but what to do in the mean time.
The next thing I did was check the pond temperature and PH. With these two factors recorded, I could use them in conjunction with the known Total Ammonia level of 0.5ppm to calculate Free Ammonia using a very handy calculator hosted by the Koi & Water Garden Society of Central New York on their website.
Some Koi keeper don't know this but the actual substance that poisons our fish is called Free Ammonia. Many test kits actually measure Total Ammonia which includes Free Ammonia and Ammonium, a harmless substance. Its the Free Ammonia that interests us, this is the bad guy that silently kills our Koi in small amounts.
If you click the link at the end of this post, there is a chart you can print off which shows how toxic ammonia actually is at specific temperatures and PH levels. I entered the figure 0.5 to calculate the level at PH 8.4 at 17.8oC. The level was 0.039 which the fish will tollerate for the 24-48 hours it will take for the filters to catch up.
By Sunday Morning, all the ammonia was mopped up and no chemicals were added, no additional water changes were made and the fish displayed no discomfort of any kind throughout Saturday.
As I said earlier, many test kits test Total ammonia and it's worth finding out which kit you have so the readings you take make sense. I could easily have panicked last weekend since a 0.5ppm level seems high at face value but armed with the knowledge that a total Ammonia reading didn't give me a complete picture, I was able to find out just how dangerous the Free Ammonia level was for the breif period of time the problem existed.
I hope you get something useful out of this thread.