Category Archives: Nitrate

Indoor Koi Pond – Trouble With Nitrates

Indoor Pond Nitrates Problem – by Doc Johnson

fish and nitrates

It’s hard to have enough artificial lighting to grow healthy algae and plants.
Without this, you can suffer an accumulation of nitrate.
In studies, high nitrate levels aren’t toxic on an acute level. Chronically, your fish will always do crappy in high nitrates. Studies on reptiles show an effect on thrift and fecundity so severe that reproduction is impaired and sometimes; prevented. High nitrate levels correlate well (and in direct proportion to) background pollution. Controlling nitrates controls background pollution.

Indoor pond nitrates problem
Indoor pond nitrates problem

This is a pan shot of the indoor pond, It was 2800 gallons in the basement of our Marietta house. It’s sixteen feet long and eight feet wide.
The fish really loved being warm all winter, but the nitrates were unreasonably high. Note the AquaDyne in the foreground. This was before they had blowers on them. That filter was completely awesome.

The overflow system I worked out: I just opened my AquaDyne sludge drain a little, allowing a small amount of water to be exiting the pond at all times. The ball valve you see in the picture replaces water all the time. I was turning over half the pond each week and still had nitrate troubles. I am a pathological overfeeder.

Indoor pond with nitrates problem – by Doc Johnson

Here are some of the fish I had at the time. By Spring, quite a number of these fish were dead due to nitrate problems which I had underestimated. Correction of the Nitrate troubles, especially via the flow through system described above, solved and stopped most of my losses.

symptoms of nitrate poisoning
The bigger ki utsuri in the picture was the first fish “spay” I ever did, and she grew twice as fast as her companions after the spay.

By concentrating light intensely on them, I was able to support some plants. However, there was no way to propagate sufficient plant growth to reduce my nitrates alone.

Indoor Koi Pond - Trouble With Nitrates

Even the prolific Duck weed was insufficient to minimize the Nitrate problems. I grew it as fast as I could, and would dip a few cups of the stuff out to feed the fish every day. Still, nitrate levels were unreasonably and unsafely high. I recommend you keep your levels under 120ppm for best results. Under 60ppm would be considered close to perfect.

This is a big problem in crowded systems but trickle water replacement, I figured out AFTER the above issue was done.

Indoor pond nitrates problem


Nitrates and What You Need To Know. Nitrates KILL Fish.

Nitrate in Aquatic Animal Health

When the cycle nears completion, you know that the Ammonia has been reduced to Nitrite, and the nitrite reduced to Nitrate.

So let’s talk a bit about nitrate.

It’s basically one of the most important plant nutrients there is. Algae will use the nitrates with a little bit of phosphate to proliferate. When the cycle finishes, your pond will usually turn “pea-green”. It’s a nitrate-party. This will starve itself out in a couple of months, or you can clear the water with a UV*.

Nitrate in Aquatic Animal Health
Nitrate in Aquatic Animal Health

You can also add some live plants in a veggie filter or in the pond itself to compete with the algae for the nitrates.

I have used UV’s and I have also disconnected my UV’s and used nothing but a vat-full of plants to reduce algae and green-water*.

Nitrate in Aquatic Animal Health

nitrate levels in ponds linked to infertilitynitrate toxicity to aquarium fishNitrates have been reported to be non toxic to fish. I am pretty sure it’s because when the scientists tested high levels of nitrates on the fish, they did not have any deaths in the first few weeks. So it was pronounced “nontoxic”.

Now, in clinical practice, I see a lot of sick fish, and in many instances where you cannot tack it down to one disease or another, often, you discover that the nitrate levels are high (Over 80ppm). Also anecdotally, people who keep their water exchanged out and maintain their nitrates well below 100 ppm generally and universally have healthier fish.

I will “stick my neck out” and maintain that high Nitrates (chronically over 100PPM) causes defects in the immune system and increases the vulnerability of the fish to disease. You will also see dilated blood vessels in the fins of fancy goldfish when the nitrate levels are high.

SHORT AND SWEET: Nitrates should be kept below 100 PPM. You can do this by encouraging the growth of plants and algae in the pond, and with partial water changes done at least every other week.

Nitrates – The Video – Summertime blockbuster