The Koi Pond Project

Filtration and the dreaded Ammonia and Nitrite

New Filter Syndrome.


Having constructed my new filter and installed all the media and filled the system with water I turned to making the water safe for my new fish.
After three days there was zero Chlorine and of course, with no fish, zero Ammonia and zero Nitrite.

I had a full new set of fish coming.
This isn't really a good idea.
If you introduce fish gradually it gives time for the filter to accommodate the changes in load.
I had bought a job lot at a job lot price and I had a deadline to collect them by.
The race was on!

Firstly I dosed the water with Ammonia solution, to simulate a large fish population.
Then I bought various filter start preparations, including, or so the labels said, the necessary bacteria.

The plan was to get the required bacteria up to speed before the fish arrived.

It was only partially successful.

It's really very simple and can be found everywhere, but here's my summary:

Fish excrete Ammonia.
Ammonia is a strong alkali and very toxic to fish.
In high pH water, "free" Ammonia exists in the water - very bad.
In low pH water, the Ammonia is present as Ammonia (Ammonium) salts and is far less hazardous.
Bacteria such as Nitrosomonas oxidise Ammonia into Nitrites (NO2).
Nitrosomonas multiply quite quickly and the high Ammonia levels should fall away quite quickly as a result.

This part happened in my new filter management plan.

Nitrites are also very toxic to fish. As the Ammonia is oxidised to Nitrite, the Ammonia levels will fall and the Nitrite levels will shoot up.
They can quickly stress the fish and weaken thier immune systems - I know, I've learnt the hard way.
Nitrites can also combine with haemoglobin in the blood in a similar way to Carbon Monoxide (brown blood disease), reducing Oxygen uptake and weakening the fish further.
Unlike Ammonia, Nitrites are much more toxic in low pH water and less toxic in high pH water.
My fish fatalities have been due to opportunistic bacterial infections taking hold because the fish are weakened with poor immune response.
To reduce the toxic effects of Nitrite, salt can be added (reduces the uptake of Nitrite in gills I believe) and repeated water changes can be made.
These help, but don't replace bacterial action and can't be succesfully used other than for very short term - again, I learnt the hard way.
Bacteria such as Nitrobacter further oxidise the Nitrite to much, much less harmful Nitrate (NO2 -> NO3).

Here is the bad news.
Unlike Nitrosomonas, Nitrobacter are very slow to multiply.

In my case, the various products I bought claining to contain live bacteria had no effect at all on Nitrite levels.
Adding a few and waiting for them to multiply won't work unless you have a very small fish load.
I spent a lot of money on Koi filter products and was unable to reduce the Nitrite levels at all.
My time was now up and I had to add my new fish to the pond and was now desperate to get the filter "mature" ASAP.
I tried yet more products to try and tackle the Nitrite (without chemical intervention), but again was failing.
Only the water changing was keeping the Nitrite below 1.0mg/litre (still way too high!).

Finally I approached a biotech company who sold me some bacteria that were:
Alive on arrival and "deployment".
In large numbers
Able to half Nitrite levels overnight.

More to come.......

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