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FAQs on Marine Water Quality involving Nitrites, Importance 

Related Articles: Nitrite, Ammonia, Nitrates, Establishing Cycling, BioFiltrationPhosphate, Silicates, Phosphate

Related FAQs: Nitrites 1Nitrites 2Nitrites 3, & FAQs on Nitrite: Science, Measure, Sources, Control, Chemical Filtrants, Troubleshooting/Fixing & Nitrates, Ammonia, Phosphate, SilicatesChemical Filtrants

Like Ammonia, nitrite presence (particularly coupled with the presence of high pH) is toxic... in any concentration. Stress... disease... death.

Royal Gramma, environment, behavior 12/21/11
I was so excited to find this website; sometimes I spend too much time reading.
 Anyway, I am concerned about a Royal Gramma.  My tank is 40 gallons. About 2
months old.  2 Tank-bred Ocellaris Clowns, 1 Canary Wrasse, 2 PJ Cardinals, 1 Royal Gramma, 2 Emerald Crabs, 1 Peppermint Shrimp, couple small blue-leg hermits, and about 12 snails.  The water conditions aren't ideal. Nitrites were a bit high, but Nitrates were lower which I found strange.
<No such thing as nitrites being a bit high, any detectable level of nitrites is a big problem and very rough/deadly to fish.>
  I have about 30 lbs of dry rock and plan on adding some live after the New Year.  Everyone was doing find until a couple days ago by small male clown started to hid underneath an overhang near where the shrimp has made home.
<Results of the poor water quality.>
This went on for a couple of days, I thought he might be stressed so I did a 25% water change; he seems to be more active now.
<Proof that the water is the problem.>
However, now the Gramma, who was always territorial over his little cove, has strayed, and last night even slept against a rock where he usually spends no more than ten minutes at.  He also would pick up and invertebrate with a shell small enough to it in his large mouth and carry them around until dropping
them which I found strange, and kind of cruel.
<Normal behavior from what I have seen from mine, actually tamer, my rips their legs off first chance he gets.>
He seems to now be rubbing against rock every now and then.  I just wanted to try and catch this early, if
it's anything at all. 
<The nitrites are the problem, that is a lot of life for such a new tank of that size, more water changes until nitrites stay at 0.>

Comment for Neale (Nitrite toxicity; RMF, stuff you may want to comment on)  10/21/08 Dear Neale, I hope you and the rest of the Crew are well. I wanted to ask you about a post I read today that you answered regarding a trigger and a tank with 0.2 ppm of nitrites. In your answer, you stated that the nitrite level was deadly and that few marine fishes tolerate any level of nitrites for long. <That was certainly my understanding... until now, perhaps!> Now, I worship WWM and particularly enjoy reading your answers every day, but everything I have read suggests that nitrite is actually harmless in marine aquaria except at almost impossible to achieve levels. For some reason that escapes me (I am no scientist), there is something about marine aquaria/fish that makes this situation much different than in freshwater aquaria/fish (in which case/es it is indeed deadly at any level). <It has long been reported (e.g., in the Interpet Manual of Fish Health) that sodium chloride (the dominant mineral in sea salt) detoxifies nitrite and nitrate, which is why it had often been used as a "tonic" to help freshwater fish in badly maintained aquaria. Extrapolating outwards from that to say marine fish are essentially unharmed by nitrite at even quite high levels does make sense.> I was wondering if you could bring some clarity to this issue--it's a frequent point of contention on the message boards. From what I have read, nitrite in marine aquaria is indeed a problem, but only because it is an indicator of an immature/inadequate bio-filter and/or an overstocked aquarium. www.reefkeeping.com/issues/2005-06/rhf/index.php Thanks! Andy <That study seems pretty conclusive, though Bob Fenner may have different opinions, and I wouldn't put myself up as any kind of marine fishkeeping guru! Most of my marine fishkeeping experience is with coldwater stuff at university, lab animals such as snapping shrimps and mantis shrimps, and some reef and fish-only display tanks I've helped maintain over the years. In my defence, my instinct in this case was that the aquarist had two fish in a tank that was far too small for them, one of which was showing clear signs of stress. My assumption would be problems with water quality, and that nitrite was detectable would seem to corroborate that. So whether or not nitrite is the thing harming this fish, it's certainly a clue that water volume, overfeeding, lack of filter capacity and so on would definitely be issues for the aquarist to review. Or put another way, nitrite in marine tanks may be comparable to pH in freshwater tanks: in itself not a critical factor, but pH is revealing about the stability and type of water chemistry conditions in the tank, and these things do indeed directly affect the fish. Anyway, fascinating stuff, and thanks for writing! Neale.> <<Mmm, I do want to chime in... a bit... and do agree that it is NOT the presence of nitrite per se that is/can be a matter of concern directly... rather than as Andy and the article state, much more so the indication that the given system is not "well-established" to "bump up" or accommodate if you will, further loading on the forward reaction of nitrification. Still the "window" of measuring, measured nitrite is useful, should be heeded as a warning to suspend feeding, further stocking. RMF>>

More Fish, More Nitrite! Hi Scott, or Bob. <Scott F. here for you!> How are you guys doing, hope you're doing wonderful. <Yes, I am! Thanks!> I wrote you a few days ago, and asked you for a few pointers on my clown trigger, and my lion fish. Well, even my tank is 120 gal, I pictured that, in a few years from now, it will be like me and my wife living in the kitchen for the rest of our lives <Very good analogy...And, as rooms go- definitely my first choice to be stuck in!> (so we decided to get a 75 gal for the lion fish only with some live rock and put that aquarium in our office. <Good idea...you and the fish will appreciate the space, believe me> But now the problem is that we fell in love with a puffer 4" (Arothron manilensis), and we bought it. Now we have 3 fishes that are doing well in the 120gal tank, but just for about 3 months till the other tank gets fully cycled and put the lion in the other one. <Okay> Now my question: I have bought these specimens because we are fairly new in saltwater keeping, and now these fish are very hardy and can forgive many of my mistakes that I will make (even if not on purpose). But for beautiful and super-hardy, and resistant that they are, BOY ARE THEY MESSY EATERS!!!, <Yes they are!> So, is there any chance with these 3 specimens for the NITRITE level to be 0.00? <Well, with a properly cycled aquarium, the nitrifying bacteria population should "catch up" with the ammonia being produced by these specimens. Unfortunately, nitrite in an aquarium is a sure sign that something is out of whack. Sounds like too many (messy) fishes added to quickly to this aquarium. You need to really slow down a bit.> Because I think it is almost impossible because the food they eat, and the way they eat. <Not impossible...simply requires careful feeding, maintenance, and patience...> If not, I already read the nitrite column on http://www.wetwebmedia.com/no2probfaqs.htm, but I do water changes ever week like 20%, I do not overfeed, and still the NITRITE level is high. <Well- a lingering high nitrite level is extremely dangerous for your fishes. I don't usually recommend this, but in this case, you may want to add one of the commercial nitrifying bacteria products to help "kick start" the cycle...As much as I'm a huge fan of regular water changes...it may be worth it to hold off a bit until the nitrite level returns to an undetectable level> How often do you recommend water changes, and how much ????. <Once a tank has been established, I like 5% water changes twice weekly> In the store that I bought all my 3 fishes (Aquatic Warehouse) (great store!!!), they sell the salt water. Do you recommend doing a massive water change 75% of the water they sell there, or doing water changes by mixing the scientific grade marine salt??? <I'd avoid the massive water changes at this point...observe nitrite levels for a few more days to see if they appear to be declining. You don't want to make a bad situation even worse by taking an impulsive action here. As far as purchasing pre-mixed water is concerned...Sure, you can do that, if it's easier and less expensive for you. But personally, I like to mix my own saltwater with RO/DI water. At least I can assure myself that the water is of consistent quality> Any advice you can give me would be appreciated.. Thank You.. <Well, my best advice is to stay the course here. The nitrite level should ultimately go down with a little patience. It's too bad that the fish have to go through this, but I think massive water changes will just prolong their exposure to this problem. Also- reexamine your filtration and husbandry techniques...With time, diligent observation, careful action, and most of all, patience-things should work out for you! Hang in there! Regards, Scott F>

Prolonged Nitrite Cycle? Hi, <Hi there! Scott F. with you today!> I have a 90 gallon tank. An Emperor 400 bio-wheel filter and a Fluval 404 canister filter. A 165 gph power head  for aeration. 220 watt power compact lighting (I leave on for 10 hours a day). A 400 watt heater. And crushed coral for substrate I have setup this tank in early December with help from my LFS. I used 9 damsels to cycle my tank. Everything seemed to be going well. By early January my ammonia levels were at 0ppm and my nitrites were high (2-5ppm hard to tell with my test kit) nitrates 0 ppm. My damsels at this time were very active and eating well.  Shortly after I had a good amount of green algae in my tank and thought it was a good sign that my cycle may be complete. When I tested again my ammonia was 0 ppm, nitrite 2-5 ppm, and nitrates 40ppm. I brought a sample of water to the LFS and the confirmed my readings and said my tank was still cycling and the nitrites must be on there way down.  They did not recommend me to do a water change. <I agree I would wait until the nitrite readings are undetectable before executing a water change> So I waited. In early February I lost 3 fish (heavy breathing, possible white spots). Once again, I brought a water sample to the LFS and I still had the high nitrites (they measured it at 4ppm) no ammonia and my nitrates were 40ppm. They said the cause of death of the fish was stress due to the high nitrites and I should not worry about treating the tank for parasites. <Well, I'd tend to agree...Unless you see signs of a parasitic illness, there is no need to treat for such a malady> This morning I lost another 3 damsels.  I noticed that they lost most of their color and their gills were red.  The other fish are sluggish and color is fading.  I did a 25% water change today.  My readings were 0 ammonia, 2-5ppm nitrites ( I need a more accurate kit) and nitrates between still at 40ppm. I have not read another article pertaining to my current problem. It seams to me with all the articles I read that my nitrites should be dropping (almost 2 months since its peak) especially that I have a considerable amount of nitrates (the tank did start out with no nitrates so I am ruling out my tap water).  My water temp is consistently 78°, Sg 1.021. Any help will be appreciated. Thanks, Jeff <Well, Jeff- hard for me to be 100% certain what is causing this cycle to take so long to complete. Lingering nitrite levels are a sign of an immature biological "filter". Sounds like something is interrupting the maturation of the system. Are you doing anything which could be killing the beneficial bacteria in the system? Any medications, household chemicals, etc? The symptoms you describe sound like poisoning of some sort- either metabolite (i.e.; chronic ammonia/nitrite) or a toxin, such as a chemical of some sort. Do re-visit your husbandry techniques, equipment function, etc. There is a logical answer for this anomaly. Do some more digging and you will find it! Good luck! Regards, Scott F.>

Nitrites hi bob, Ok I tested my water in my 240 F.O tank. Here's the results ammonia= 0 nitrites= <0.3mg/l - 0.3 mg/l nitrates = 25 mg/l My question is that on the nitrites the color chart for the test kit doesn't start from 0 it starts from <0.3 mg/l to 3.3-33mg/l So does that mean that nitrites are ALWAYS present in a healthy system???  <No my friend... should be undetectable... as in zero ppm or mg/l in a fully "cycled" up and going system... Any appreciable nitrite (or ammonia for the matter) is cause for concern... either the system is insufficiently filtered (aerated, circulated), and/or over/mis-fed, something is dead/dying in it, it's over-crowded/mis-stocked... Please read: http://wetwebmedia.com/no2probfaqs.htm> And also do you think its a good time now to hook up my ozone generator to my skimmer??? <Yes> My tank has been running for 4 weeks now. Thanks again your fan, Lee <Direct your focus, ability, interest into study here... You'll soon be answering these queries (thanks in advance!). Bob Fenner>

Re: nitrites Bob, my Tetra Nitrite test kit graph/chart STARTS at <0.3 mg/l. When I testedmy water it was at the <0.3mg/l. Which is the lowest on their chart. This is what the Tetra test kit instruction says. Ill punch it in for you in exact words . " Ideally nitrite levels should be kept below 0.8mg/l." <Hmm, do agree... I generally state "1.0 ppm" out of laziness, assuredness that this value is most easily remembered...> " If nitrite levels is above 1.6mg/l, carry out a partial water change".  <Well... this doesn't seem logical (to me obviously)... I caution folks to do such a change at or above "1.0 ppm" (or mg/l)... for the same expedients mentioned above> "Biologically active and efficient filtration will keep nitrite levels at a very low and safe level". So to me Bob it sounds like Tetra is saying that there will ALWAYS be some presents in nitrites. Yet you told me that nitrites should be at 0mg/l. What is your opinion regards to this . Your big fan. <Still a fan? Well... I'm still of the opinion that they (nitrites) should be zip, zero, zilch... Do query the various electronic bulletin boards, chatforums (here's WWM's: http://talk.wetwebfotos.com/), or published works... S/b nada, none... Bob Fenner, who IS a big fan of Tetra/Pfizer... but not their English inserts. labeling at times.> Lee

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