Nitrite in Cycling Tanks: Treating with Salt

[cvermeulen]

OK, I was doing some research today, as I have a tank that is almost finished cycling, and I have to go away for a few days. Obviously I'm concerned about my fish dying while I'm gone.

I ran across this article: http://www.aces.edu/dept/fisheries/aquaculture/pdf/462fs.pdf

This is a very interesting write up, and I find it very useful. It basically suggests that the Cl- ion from adding regular salt to your aquarium will protect your fish from Nitrite poisoning. Now, this is not to suggest you should just let the nitrite build up and chuck a bunch of salt in there, but it's particularly useful during the nitrite spiking phase, as the nitrite is said to be dangerous above 0.1-0.3ppm depending on who you talk to. So, if you have a fish producing 10ppm of nitrogen every day, you have a real problem. Right now I'm seeing an accumulation of around 0.5ppm per day of nitrite, so if I add something like 100ppm of salt (way less than typical aquarium salt dosages), my sole occupant should be safe from brown blood disease even if the nitrite builds as high as 5ppm while I am away.

Does anyone take issue with the chemistry/biology here? It does seem a bit too good to be true, but it makes sense - fish farmers can't do waterchanges when a seasonal change disrupts their biofilter. It also puts some sense to the claims of products like "Prime" that say they detoxify nitrite, but they won't tell you how. Answer is they don't do anything to the nitrite, they just have some Cl- ions in solution that get absorbed by the fish's gills instead of the harmful NO2- ion

 

[brianp]

Forget the salt. Toss in a bottle of Seachem Stability and go on your trip.

 

[cvermeulen]

Forget the salt. Toss in a bottle of Seachem Stability and go on your trip.

Well thanks for that but...

My point was to bring to light an explanation for something I've seen a LOT of questions about - how do water conditioners detoxify nitrite? Answer: Chloride ions block the absorption of NO2- but the fish's gills. My secondary objection was to spark some educated input/debate on the point, but it doesn't look like there is a lot of interest :/

Also, I'm lucky to be able to get prime where I live, so I doubt very much I'll find stability - but I will read up on it.

 

[brianp]

I see. I'll tell you what I know.

Nitrite will cross the gill surface and enter the blood. Once there, it will bind to the fish hemoglobin to form "methemoglobin". Methemoglobin is incapable of binding and transporting oxygen, so your fish will essentially suffocate.

Nitrite (NO2--) and chloride (Cl-) both carry negatvie charges. I have never done this, but my recollection is that a concentration of 0.3-0.5 % NaCl added to the aquarium water will prevent the uptake of nitrite at the gill surface. Presumably, this has something to do with the chloride saturating whatever mechanism is responsible for nitrite uptake. I think that freshwater fish blood has a total salt concentration of about 1% but this is irrelevant once the nitrite has entered the bloodstream, because the chloride will not outcompete the nitrite for binding to the fish hemoglobin. So, the strategy is to prevent the nitrite from getting into the blood. 0.3-0.5% means that you would have to add 11.4-19 grams of NaCl per gallon of aquarium water. You may want to double-check my math, since I'm doing this on-the-fly.

 

[JakeH]

I don't know enough to debate the chemistry or biology involved, but I thought it was pretty well known that salt helps detoxify nitrite. Anyway, I don't think a chemical or salt is a very good idea for your particular situation. I'm sure its not easy to find there, but can you get chemi-pure or Purigen or NitraZorb or any kind of exchange resin? It might slow down your cycle a bit, but it would probably work for the whole time you're gone... Just my .02...

 

[Conner]

I don't know enough to debate the chemistry or biology involved, but I thought it was pretty well known that salt helps detoxify nitrite. Anyway, I don't think a chemical or salt is a very good idea for your particular situation. I'm sure its not easy to find there, but can you get chemi-pure or Purigen or NitraZorb or any kind of exchange resin? It might slow down your cycle a bit, but it would probably work for the whole time you're gone... Just my .02...

I think part of the point of the salt is that it won't slow down the cycle of the aquarium, but it prevents the fish from suffering the effects of that cycling (i.e. nitrite poisoning). So if he doses the correct amount of salt, the tank will continue to cycle while he's gone, but he won't have to worry about the fish being poisoned and dying before he gets back.

Sounds like good science to me, but I haven't really studied this kind of situation in depth before.

 

[cvermeulen]

a concentration of 0.3-0.5 % NaCl added to the aquarium water will prevent the uptake of nitrite at the gill surface.

The article I linked there suggests a concentration of anything over 10x the concentration of nitrite should be sufficient. So if you have 5ppm Nitrite 50ppm of salt should be enough. Many fish farmers keep a baseline of 100ppm of Cl- in the water (.01%) just for insurance sake.

As aquarists though we're not looking so much at our fish just not dying, we want them to thrive, so I wasn't sure how much stock to place in this article.

Anyway for my particular situation I will go to the little hole in the wall petstore tomorrow and see what they have, but I'll probably apply more than one tactic. I was only citing that as an example though - I'd personally never heard of salt detoxifying nitrite before, and I always had trouble believing that water conditioners actually detoxified it.

 

[HarleyK]

Howdy,

The article specifies that you know the Cl- concentration in your water in order to calculate the amount you have to add. Very few of us keep track of that...

Secondly, adding salt should be decided based on the species you keep. While I assume you don't put the most sensitive species in a cycling tank, I also want to point out that some fare better with salt than others.

Lastly, I think there is nothing just like a good water change. It's not going to ruin your cycle, though it my drag it out a day or two. So what?! Then a few days without feeding while you're gone will be no problem at all.

HarleyK

 

[JakeH]

Howdy,

The article specifies that you know the Cl- concentration in your water in order to calculate the amount you have to add. Very few of us keep track of that...

Secondly, adding salt should be decided based on the species you keep. While I assume you don't put the most sensitive species in a cycling tank, I also want to point out that some fare better with salt than others.

Lastly, I think there is nothing just like a good water change. It's not going to ruin your cycle, though it my drag it out a day or two. So what?! Then a few days without feeding while you're gone will be no problem at all.

HarleyK

Tough to argue with logic like that... +1

 

[cvermeulen]

Howdy,

The article specifies that you know the Cl- concentration in your water in order to calculate the amount you have to add. Very few of us keep track of that...

OK True, but I think it's reasonably safe to assume it is zero in most instances. The amount required to achieve 100ppm (100mg/l) Cl- in a 800L (200gl) tank is 100mg/L*800L*1/0.66 (0.66 is the mass percentage that Salt is of Cl-). This works out to about 14g, or one tablespoon. Aquarium salt is typically added in dosages of 40X this much. The reason that article suggests you calculate it that way is they are talking about millions of gallons. A few extra Tonnes of salt is a big added cost, so taking the existing Cl- into account is important.

Secondly, adding salt should be decided based on the species you keep. While I assume you don't put the most sensitive species in a cycling tank, I also want to point out that some fare better with salt than others.

Well your tank may be cycling for any number of reasons, not all of them start-up. I must again point to the extremely low concentrations recommended though - even fish that don't like salt should hardly notice 100ppm

Lastly, I think there is nothing just like a good water change. It's not going to ruin your cycle, though it my drag it out a day or two. So what?! Then a few days without feeding while you're gone will be no problem at all.

I've been doing 75% waterchanges daily to mitigate the ammonia and nitrite. I'm in the unfortunate situation of having to cycle with a very large fish. He also has not eaten in 3 weeks, but the nitrate reading in the tank after 24 hours is 7-10ppm. Luckily the tank was partially cycled when I put him in there and for whatever reason I appear to have bypassed the huge nitrite spikes (highest yet is 0.8ppm).

Anyway, there are a lot of reasons you might have a problem with nitrite, and you may not be able to do frequent enough waterchanges to offset the effects. Seems like cheap insurance to throw in a pinch of salt to me.