I have inherited a Koi pond when moving in. I have lost 3 large Koi over the last month and I have tested the pond and the PH is sitting at about 5 - 5.5. I know this is too low. POnd size is 16000 litres. How much Bicarbonate of Soda should I add and how quickly should I see the PH going up?

You can about 500 grams (1 box) then check the level again the next day. Do not add to much of it to often give atleast a day for it to settle into the enviroment.... And DO NOT test the PH...that is pointless as the PH will settle to where it should be for the pond in question rather test the Total Alkalinity (TA). The TA should be atleast 100. The TA will control the fluctuations of the PH. See this article http://www.koiadventures.co.za/Home.aspx?Page=UsrGeneric.ascx&Rec=278

Hi MG

I am quite sure that the problem is your PH. You probably know that the PH should be between 7 and 8.5. The difference between your 5 and the 7 required is 20 fold.

You Koi suffers from Acidosis and your koi probably has increased gill movement and an erratic swim pattern.

Bi carb will solve your problem temporarily, but the PH will probably decline again. You will have to also look for answers why the PH is low, and rectify the cause.

The low PH might be due to excessive algae bloom or an excessive plant growth that will take out the Carbon dioxide and Nitrates which will contribute to acidic conditions. A dirty pond will also cause a low PH.

Your long term solution: Add oyster shells and a few concrete building blocks to your filter, clean your pond and filter more regularly if there is any built up of sludge and increase your aeration.

Rectify your PH immediately with BiCarb, but remember to do that gradually. A sudden change will be more stressful for the koi than doing nothing.