If you test your kH and it falls below the minimum 80 PPM, then you need to raise it gradually. This is done by simply adding sodium bicarbonate (baking soda). But, remember the importance of keeping the fish's environment stable? Well, it is for this reason that you should never raise your kH more than 20 PPM per
24-hour period. For example, if your kH was 40 PPM, you will have to add the baking soda twice over a 48-hour period, with each addition being 24 hours apart, to get it to the minimum 80 PPM.
NOTE: You should recheck your kH reading 24 hours after each addition of baking soda to make sure it is not increasing more than desired due to some sort of miscalculation on your part, such as pond gallonage or baking soda measurement, etc. Also, you must be aware that baking soda has a consistent pH of 8.4, and will raise the pH of your pond to this figure if it is below that. Also, be sure to check your ammonia in your pond before the addition of baking soda. Ammonia becomes much more toxic as the pH rises above the neutral reading of 7,so if you have any ammonia in your pond I would not recommend the addition of the baking soda until you get the ammonia to 0 ppm.
The general rule of thumb for increasing your kH is by 20 PPM increments every 24 hours, by adding ½ cup of baking soda per every 4,000 L of pond water. For smaller volumes you would add about 1/4 TEASPOON for every 40L of water to raise the kH 20 PPM. Remember, however, to recheck your kH and pH 24 hours after each addition. It is also wise to keep an eye on your fish for any adverse reactions during this period, but if you have calculated correctly, there should be none. You would have to be off tenfold to really see a negative reaction from the fish.
CAN ANY ONE TELL ME HOW TO RAISE MY KH OF 89 BUT LOWER THE 8.5pH IN MY POND SINCE BICARB WILL KEEP pH AT 8.4. All the 'baddies' behaves worse at high pH levels, or am I wrong or just to much in a hurry since the pond is not fully matured yet