# [Wet Thumb Forum]-Excessive Nitrates in a Low Tech?



## imported_Poe835 (Oct 20, 2003)

Has anyone experienced excess nitrates in a low tech without CO2 injection? I have discus in my tank even with 2wpg/CO2 injection, so I imagine that it would be even worse in a low light, non CO2 tank. How does one deal with high nitrates in a low tech tank? Has anyone experience this?

thanks


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## imported_Poe835 (Oct 20, 2003)

Has anyone experienced excess nitrates in a low tech without CO2 injection? I have discus in my tank even with 2wpg/CO2 injection, so I imagine that it would be even worse in a low light, non CO2 tank. How does one deal with high nitrates in a low tech tank? Has anyone experience this?

thanks


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## anonapersona (Mar 11, 2004)

I suppose you'll need to do more and/or larger water changes.


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## imported_Poe835 (Oct 20, 2003)

But the low tech method shouldn't involve frequent water changes....


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## Robert Hudson (Feb 5, 2004)

Well if you are putting a strain on the bio system by either having too many fish for the size tank, very large fish that have a heavier bio lode, or if you over feed your fish, then you may have higher nitrate levels. Low tech or high tech, you need to look for the cause and treat it.

In an earlier thread Diana talked about her finding high nitrate levels in one of her tanks, and how she did a water change to relieve the problem.


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## DataGuru (Mar 11, 2005)

But I also remember her saying that she doesn't believe the nitrAtes are that toxic.

Betty


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## dwalstad (Apr 14, 2006)

Again, I don't think that nitrates are toxic. My 50 gal just registered 100 ppm and fish are doing fine.

I know I sound cavalier, but when I was doing sickle cell anemia studies in human red blood cells, we often would substitute sodium nitrate for sodium chloride as the bathing medium for the red blood cells (We were studying chloride transport mechanisms in cells). Nitrate was totally non-toxic as a substitute for chloride. 

I believe that amy problems with nitrates are secondary effects. If your system is too anaerobic, you might get bacterial conversion of nitrates to nitrites, which are very toxic. But nitrates by themselves, I doubt have any toxicity.


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## Robert Hudson (Feb 5, 2004)

I don't quite understand that because I have always been taught from way back that nitrate levels of 20ppm or higher are considered dangerous to fish, that it can stress fish, interfere with breeding, reproduction, gills, which leads to death and many fish I have been told are sensitive to nitrate levels, including Discus, Apistogrammas, and many soft water fish. I have been told Neon tetras are particularly sensitive and is why they are so hard to keep for most beginners. I have also been trold that fish most often contract diseases like ICH or Hole in the head due to over stress from poor water conditions. But I am a long way from being any sort of authoritive on the subject.

But regardless of whether anyone contends they are toxic or not, if the levels are higher than what you want them to be, the only way to lower the nitrate level is with water changes, the only quick way. Otherwise, you need to determin what is causing the high nitrate levels and modify it, ie fish over crowding, over feeding... or you can increase the growth rate of the plants so they consume nitrate faster which would require more intensive light and C02 supplimentation, ie high tech. I think most low tech plant people keep a very conservative number of fish so as to not overload the balance, and rarely see high nitrate levels. At least that would be my take on it!


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## dwalstad (Apr 14, 2006)

I was just passing through library today and serendipitously got the toxicity values (LC50) for nitrates from separate scientific studies for the 5 following fish species.

Salmon 1,310 ppm
Rainbow Trout 1,360 ppm
Channel catfish 1,400 ppm
Bluegill 420-2000 ppm
Guppy 180-200 ppm

These values are in the textbook 'Fundamentals of Aquatic Toxicology' and the author states that nitrates are "considered to be essentially non-toxic". I would agree.

As to reducing nitrates in aquariums, water changes aren't the only mechanism. I found that soil and/or mulm (no plants) will remove nitrates from the water. I'll talk about this at the AGA Convention.

There's a lot of folklore in the aquarium hobby. I know that my Rainbowfish do fine at 100 ppm nitrates. I think that it's secondary factors (introducing diseased fish without quarantine, salt buildup along with nitrates from infrequent water changes, filthy tanks) that sometimes accompany high nitrate levels. 

I let fish behavior (eating or not?) and plant growth (growing or not?) determine what water chemistry is detrimental. If my fish don't eat, then I immediately take corrective action- change water, clean filter, and add fresh carbon to filter.


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## imported_Poe835 (Oct 20, 2003)

Thanks Diana, for pulling out those numbers. My tank (30 gal, heavily planted with two 3" discus and two 2" clown loaches and a couple cardinal tetras) is seeing about 40-50 ppm nitrates. Are high nitrates (>30 ppm, say) common among low tech planted tanks? Have you seen any effect of high nitrates affecting plant growth by inhibiting uptake of other nutrients?

thanks again


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## imported_shalu (Feb 13, 2004)

I would have to say "good luck growing them out to big beautiful discus in such a tank", but I am afraid they are likely to be stunted.


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## dwalstad (Apr 14, 2006)

> quote:
> 
> Originally posted by Poe835:
> Thanks Diana, for pulling out those numbers. My tank (30 gal, heavily planted with two 3" discus and two 2" clown loaches and a couple cardinal tetras) is seeing about 40-50 ppm nitrates. Are high nitrates (>30 ppm, say) common among low tech planted tanks? Have you seen any effect of high nitrates affecting plant growth by inhibiting uptake of other nutrients?
> ...


Hi Poe 835,

There is nothing in scientific literature that suggests that nitrates would inhibit uptake of other nutrients-- by plants or fish.

My tanks, in terms of nitrate levels, have varied wildly over the last 15 years with little correlation to fish health. I have changed filtration systems, which may have greatly influenced nitrate levels. Right now I keep my tanks more aerobic (cleaner and less debris) than in the past. The tanks seem to show more nitrates. That isn't too surprising, as aerobic ecosystems will inevitably accumulate nitrates. Tanks with debris and anaerobic pockets of mulm that I had in the past will favor denitrification processes that remove nitrates. Either one is fine by me (and my fish).

While I could be wrong, I don't think that 50-100 ppm Nitrates will harm your Discus. Let fish apetite (not testkits) guide you.


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## skylsdale (Jun 2, 2004)

> quote:
> 
> There's a lot of folklore in the aquarium hobby.


That's the understatement of the year.


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## dwalstad (Apr 14, 2006)

Although nitrates themselves are not toxic, there is one potential problem with high nitrates in aquariums that hobbyist should be aware of.

In dirty tank with debris and anaerobic pockets, nitrates may be easily converted to nitrites, which are very toxic. Nitrites may cause all the problems (sick, diseased fish) that Robert described earlier. Nitrites are formed from harmless nitrates by a common bacterial process called "Nitrate Respiration" (see p. 65 in my book). 

Fortunately, plants seem to like nitrites (almost as much as they like ammonia). This is fortunate, indeed. Also, nitrifying bacteria will remove nitrites.

So if your tanks accumulate nitrates, I would get a nitrite test kit and make sure that nitrites are undetectable. Make sure your plants are growing (not just sitting there), and don't let too much debris accumulate.

The most important indicator, though, is fish apetite. The few times that I found my fish not fighting over their flakefood, I measured problem levels of nitrites.


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## WolverineFan (Nov 28, 2004)

Sorry for digging up an old thread but if I recall correctly LC50 is the point at which 50% of the fish in the tank have died. Which means that fish started to die at a lower level (sometimes much lower). The first four fish cited are rarely kept in aquariums leaving the guppy as the only example of a commonly kept fish. An LC50 of 180-220 ppm means that some fish were dying at much lower levels (nearer to what a hobbyist might see). Just my two cents.


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## dwalstad (Apr 14, 2006)

I don't mind your digging up an old post, because the nitrate debate is an important one.

Although Salmon and Rainbow trout are not kept in aquariums, I would not dismiss scientific data showing that nitrates are virtually non-toxic to these fish. And I question the guppy study. Nitrates can be easily converted to nitrites, which are very toxic. Thus, scientific studies must be done carefully AND hobbyists must be careful in concluding that nitrates, per se, are toxic.

I have seen my Rainbowfish robust and jumping out of water for food in tanks with 80 to 100 ppm nitrates. I believe that nitrates are like chlorides-- just another harmless anion. 

Again, bottom line- let fish apetite guide you. If the fish are eating, then it doesn't matter what the nitrate levels are. If the fish aren't eating, only then do you need to worry about nitrates, water changes, LC50s, etc.


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## WolverineFan (Nov 28, 2004)

Hi Diana, The fact that nitrates can be converted back to nitrites is not a well known fact. I appreciate you reminding me of it.


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