nitrates and long term exposure.

[Russ Little Pond]

Much has been said and written about how toxic nitrates are at high levels (75/100mg/l) for long periods of time and how that toxin damages fish, my question is, what is a long period of exposure to nitrates at 75/100mg/l.

I look forward to your thoughts.

[Manky Sanke]

Russ,

I can't define how long would be regarded as a long period but I can give some information about the effect of nitrate on koi.

It has long been said by koi breeders that nitrate has a detrimental effect on koi growth and skin quality but, until recently, there were never any concrete facts or research that we could point to in order to back up this belief. In fact, although it doesn’t seem to be widely known, the research into the negative effects of nitrate on koi has already been done.

After reading through some old and almost forgotten articles, Kevin Novak PhD discovered that, around 15 years ago, in a research paper for the ZNA, Takayuki Izeki wrote about his research into the effect of nitrate on the shiroji (white) of kohaku.

Kevin designed the anoxic filtration system that completely eliminates nitrate as a by-product of removing ammonia from a pond and I've been helping him publicise the system so he sent me the information and I've passed it on it at every opportunity.

Takayuki san found that the maximum acceptable level of nitrate for koi keeping should be 15 mg/L, saying: "anything more than this and the skin gradually begins to deteriorate but will improve again if the concentration is reduced."

He also said that if the pond nitrate level could be kept lower than 5 mg/L, "the skin becomes so white it virtually shines". His research found that the negative effect of nitrate was caused by it reducing the koi’s ability to discharge metabolic toxins from its body and that this resulted in these metabolic wastes building up in the skin.

There were no time limits stated but, I would guess that if nitrate prevents metabolic toxins from being discharged and causes them to build up in the skin then the effect starts with an imperceptible decrease in skin quality on day one and, as these toxins continue to accumulate, the reduction in skin quality increases by tiny amounts each day.

I would think that a similar question would be "how many cigarettes can you smoke and over what period before smoking can be said to have caused an effect on your health". Obviously a lot of cigarettes over many months or years will have a greater effect but, if you measure health to a fine enough degree, you could say that the first packet will have begun the process by causing a very small effect.

I'm not sure if that helps but that's how I rationalise it in my mind.

[Duncan]

Hi

I would not get to sexed up about nitrate simply because it is the less toxic parameter of a recirculation fish pond system and last there is very little knowledge in the written world of the toxic effects of NO3.

Nitrate is an ionized form of nitrite and is the end product in the process of nitrification of ammonia;. Although Nitrite (NO2) is converted relatively quickly to nitrate it become a problem in a koi pond because it’s being produced on a constant basis so the fish are continually exposed to it in one concentration or another but rest assured no matter how well you maintain your pond your fish will be constantly bombarded by the continual exposure to NO3.

As I say there is very little literature on the what if any the adverse effects are of Nitrate in a recirculating system and its not thought to have adverse effects. For instance there are recorded instances of Salmon being raised in nitrate concentrations of 1500mg/l with no ill effects on the salmon yet by the same token there are recorded instances of 1600mg/l being toxic to gold fish but nobody says what these toxic effects are!

OATA specify fish should be subject to no more than 50mg/L but fail to say why? When we have recorded levels of keeping salmon in 1500mg/L with no ill effect

I have head so called koi experts wax on for years about how dangerous high levels of Nitrate are but fail with any real science to say what will happen if you exceed these levels when aquaculture have no choice than to raise food fish in exceptionally high levels of Nitrate. Some will say colour suffers Growth fails and body shape suffers when in truth there is no science to support this.

So where does that leave us? If your pond produces 1kg of TAN (ammonia/nitrogen) per day you will by process be producing 1kg of Nitrate per day and you have to look at Nitrate if nothing else as a potential food source. This food source will not only be available for blanket weed which you will be dogged with if you have high nitrate levels, but what you probably have not considered is certain pathogenic bacteria are capable of denitrification some pseudomonas and bacillus will do well in a high nitrate environment this will encourage anaerobic pockets on your filters and pond and obviously these bacteria will be there to infect fish.


What I would say is apply some logic to it, being as koi will be exposed to nitrate at a constantly at relatively high levels it make sense to me to limit this exposure by as much as is humanly possible to you by water change outs, obviously for people on a water meter this may not be possible, what I would say the these folks is don’t get too sexed up about not being able to do this, look at the evidence with salmon and gold fish it no big deal if you cant

Any direct effect on fish of high nitrate is more likely to be as a stressor by the fact the fish is continually being subjected to something other than trace levels and we all know what stress can lead to there should be no need to bench race the effects of stress here on koiquest, what I will say is this, I have not kept koi now for over two years this has given me time to reflect on how my progressed over the years I did keep koi, and it should come as no secret top many of you I was a big advocator of using RO water and for many years I was constantly trickling in and out RO water, this of course led to virtually undetectable levels of ammonia, nitrite, NITRATE, sub 100ppm KH and TDS and no detectable GH. Did I gain anything by this over the years?

I have to say after two years reflection no! I never grew a huge fish. I still suffered from shimmies, colour was not bad but nothing exceptional and I had the same blanket weed problems as most importantly I still had health problems,

So what do you take from this? I would say again don’t get too sexed up about it I have a good library on the science of fish keeping and there is no real evidence of the adverse effects if any of high nitrate and if you want a figure to work with I would say whatever you can get away with and your predicament dictates

[Russ Little Pond]

Thank you both for two in depth to the point replies.

This information has answered many questions, as for blanket weed its all gone, as winter was left behind heading for summer and the water started to warm blanket weed decreased nitrates increased from 12mg/l to 100mg/l today my pond is blanket weed free, fish are showing no signs of stress.

Thank you both.