I am assuming you really do mean nitrate and not nitrite. Many folks confuse these.

Nitrate levels up to 40 PPM really aren't a big deal. Floating plants love nitrate, and will quickly use it up is you have enough healthy plants. As long as your floating plants have enough potash and micro-nutrients they will consume the nitrate. Do you have floating plants like water hyacinth, duck weed, azolla, or maybe watercress. How do they look?

The baking soda has nothing to do with the nitrate levels.

I have hyacinth....they are small, not growing too much. On another post you told to try some iron for them. I am going to pick some up tonight and try it. I was thinking if I get the Hyacinths going it would help....Thanks.

One way to reduce nitrate is through a water change, unless your source water is high in nitrate in the first place. Have you had an algae bloom at all?

NitrAte is part of the normal pond cycle. Fish excrete ammonia. Beneficial bacteria break down the ammonia into nitrItes. Other beneficial bacterial break down the nitrItes into nitrAtes. Algae and other plant life use the nitrAtes.

The purpose of adding baking soda is to increase the kH of the water. A very low kH can possibly (not probably, just possibly) lead to pH crashes, which can kill koi.

Ammonia and nitrIte are toxic and should be at zero or close to it at all times. NitrAte in moderate amounts, (less than 40ppm) is ok.

I had a nitrAte problem a month back. Threw some WH in there and BAM; no more nitrAte problem....

But the next morning..... fish got jiggy and BAM! fish eggs and foam problem (ammonia).

Bless those fishies...

LP

The easy way to say Water Hyacinths. And you don't have to remember how to spell it. Glenda