Thread: Kh of 2 and persistent low nitrite

Got a relatively new, less than 3 months, grow on set up. Its 1500 litres roughly growing on 10 6-8 inch koi. Running on an easy pod into an oase biosmart 3600. Seeded all the filters with some mature media and never had a single showing of ammonia but always had a slight nitrite reading. Ph has been a constant 7.5. Kh is low were i am from the tap at 2. Also kh stays around 2 in the pond as i trickle in around 300-400 litres a day.

Im happy keeping a low kh as im on top of that. I may buffer if ph dips but all doing well and fish look active and healthy.

By now i really expected the nitrite to settle but it just isnt. Is there any chance the low kh maybe stopping the bacteria developing and not fully taking care of the nitrite? To clarify as well ive been showing nitrate at low levels since week 1 as well.

Any advice greatly appreciated.

Hi. You have to give it more time to settle, adjust the food etc. What are you using to test?

Originally Posted by Maddog1

Hi. You have to give it more time to settle, adjust the food etc. What are you using to test?

Ive actually upped the food while weathers still good to take advantage of the summer months for growth. Using a dropper test kit, tested with 2 different kits and same results.

Originally Posted by K3vinjam3s

Ive actually upped the food while weathers still good to take advantage of the summer months for growth. Using a dropper test kit, tested with 2 different kits and same results.

My Fish are in a temp pool at the moment, I have a fast tickle in, about 20 % a day. And feed enough to keep them happy. Slight nitrite reading, but no flashing etc. They look very healthy, I just keep an eye on it.

They koi are all 6-8" and will only grow slow as the water is not heated. Also they are in here to grow on before going into a bigger pond next year.

My main concern is just the lingering low nitrites.

You could use some Zodlite in a filter bag which absorbs it and then recharge by putting in salt for 24 hours.

Also I’ve had test kits give bad readings. So if it’s an old kit, it’s worth replacing it.

Maddog nailed it in his post.

Some set ups just take ages for nitrite to clear up.

One of my ponds took 9 Months of consistent high nitrites, then one December morning completely out of the blue it was zero.

As for the stocking levels and water volume, obviously not suitable on a longer term basis but as a grow-on that will receive constant attention, fresh water and maintenance it will be fine, just don't get lazy as things can turn bad fast. When I had a small grow on with heavy feeding I was having to change 50% of the water every day just to stop the KH going to zero (and it was 9-11 out of the tap!). The biggest of those Koi hit 35cm at around 9 months old.