I closed my 8,000 gal pond down last Nov. with a ph 7.8-8.0 and kh at about 120. All well and good. Only 10 1-3 year old koi. This last warm spell ice melted temp rose to 50 degrees. Fish seemed happy about it. Started just my skimmer to get a jump on spring cleaning.....The bad news.... Tested water. Ph 9.5,
kh about 30 ppm. Fish didn't seem stressed at all, all other tests normal, nitrite , nitrate , ammonia.
Have so far, in a panic, added I & 1/2 bottles of vinegar. Didn't have much effect, only lowered ph by about.02. Added 1&1/2 lbs of bicarbonate. Kh up to about 50. E-mailed Ned 2 days ago....No reply. Did some more research on my own and found this. Don't use vinegar to adjust ph. Use hydrochloric or muriatic as this, done right, has no effect on the fish. Vinegar, it said, in too much of a qty can severely irritate them. Don't adjust kh too fast while trying to raise or lower ph as it acts as a buffer and makes it too hard to move ph levels. I am currently adding small amounts of acid to my settling pond (125 gals.) and running a very small pump from pond into it and letting it flow into main pond in mixed state. I am doing this over a matter of days so as not to shock the fish.
If anyone has any other warnings or ideas please help. I would appreciate anyones help on why this happened in the first place. I can figure severe drop in kh let the ph go out, But don't know why.