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FAQs on Freshwater Quality involving Nitrites: Sources 

Related Articles: Nitrites in Freshwater Aquariums, Nitrates in Freshwater Aquariums, Biological Filtration, Establishing Cycling, Freshwater Filtration, Know Your Filter Media, A Concise Guide to Your Options by Neale Monks, Setting up a Freshwater Aquarium, Tips for BeginnersWater Quality and Freshwater Aquariums

Related FAQs: Importance, Science, Measure, Control, Chemical Filtrants, Troubleshooting/Fixing, & Ammonia, FW Nitrates, Freshwater Nutrient Cycling, Establishing Cycling 1,

From stalled cycling, kill off of beneficial microbes (via medications, water conditioners...), excess feeding, insufficient filtration, tap/source water

Goldfish Filtration: Trickle or Canister (RMF, any thoughts?)   7/6/10
Hi there, I am hoping you can give me some guidance on filtration for my goldfish.
<Fire away.>
I currently have a 50 gallon glass tank with three good-sized Orandas, a tele, and a small Ranchu and am running 2 Eheim 2217 canister filters. I am thinking of upgrading to an almost 100 (U.S.) gallon acrylic tank, and the maker wants to install an overflow box and drill the tank.
Re the new tank, I am debating whether I want to move to a trickle filter or just add another canister to the system. I have had mixed advice on trickle filters for goldfish and am unclear if they provide sufficient tank turnover/surface agitation.
<Either should work fine if properly configured and large enough for the job. If "marine grade" in terms of size, turnover rate it should be fine. I have kept big cichlids in ex-marine tanks with trickle filters, and didn't observe any real problems.>
On the other hand, I have heard that trickle systems are cleaner looking, lower maintenance, and are superior in terms of beneficial bacteria.
<Six of one, half a dozen of the other. Canisters are easier to maintain in some ways because you can unplug them, take them into the kitchen or patio, rinse off the media easily, and then put them back when you're done. Not
all trickle filters are equal, but assuming yours has a big sponge at the front for mechanical filtration, removing and cleaning that sponge should be easy enough. Getting at the plastic balls isn't always so easy. On balance though, I don't find that either has any "killer" feature that renders the other one obsolete.>
However, it also seems that a closed system, i.e., the canister filters, may be "safer" in the event of power outages (which happen where I live), don't need to be topped off, etc., and of course I already have an investment here.
<Oh, and the contrary, canister filters are VERY sensitive to power outages because air can't get in. Within 20 minutes (supposedly) the oxygen inside the canister filter is gone, and the bacteria start dying, or at least becoming dormant. That's why it's so important to crack open your canister during a power outage and place the filter media in a bucket or basin of aquarium water, so air can get to the media more easily. On the other hand, if the power is gone for too long, a trickle filter can dry out, and again, that will kill, or at least make dormant, the bacteria. I would recommend you read this article on surviving power outages:
While freshwater fish are much more tolerant than marines of this sort of crisis, it's as well to be prepared.>
However, three canisters (unless I spend hundreds to get a super high capacity one to replace what I have) may be unwieldy.
<Indeed. There are jumbo canisters like the Fluval FX5 that may or may not suit your budget.>
If I do keep/expand the canister system, can I incorporate it into the overflow box somehow?
(The problem with an acrylic tank is it has bracing at the top, so not so easy to hang the spray bars, etc, over the top--but I need an acrylic tank as I move frequently and I have found that glass tanks and movers don't mix.)
<Nothing wrong with connecting the inlet and outlet to the sump, and placing the canister inside the cabinet beneath the tank.>
What would you recommend for goldies in the larger, new tank?
<Either; see above.>
Finally, if I incorporate the overflow box with either system, where should I position it and should I have one or two?
<In theory, the more uniform the water flow, the better. But with that said, fancy Goldfish aren't strong swimmers and won't appreciate the very high turnover rates used in marine tanks. You're looking at about 6 times the volume of the tank per hour, whereas marine tanks will be 10 times or more. Check the size of the pump being used, and ideally find one with an adjustable flow rate. Failing that, I'd have the inlet at one end, the outflow at the other, so the Goldfish could swim to faster or slower areas as they preferred.>
And, where should the tank be drilled?
<Do read here:
Especially the "Plumbing and Fitting Size:" and "Through-Put Fittings:"
sections. Note what Bob says about having large, numerous holes so there's redundancy there in case of blockages or underestimating. At the same time, I wouldn't worry unduly about getting this "perfect", and whatever is
recommend for marines by the manufacturer should be adequate for Goldfish.
The major difference is that Goldfish produce more solid waste, so mechanical filtration is even more crucial than in a marine tank.>
I believe am going to have the tank made to these dimensions: 60" long x 21" wide x 18" high. I would really appreciate your advice as having this tank made is quite an investment and I want to make the best choices I can.
Many thanks!
<Glad to help. Cheers, Neale.> <<I do agree with what you've presented Neale... and would add/reinforce that trickle filters tend to "over-drive" nitrification, producing more nitrate than other modes of filtration/gear... And such filters are noisier, create more smell, and take more power to operate. If it were me/mine, I'd continue to operate this new system on the (perhaps larger) Eheim canister filters (which is what I use on my fancy goldfish systems). Bob Fenner>>
Re: Goldfish Filtration: Trickle or Canister (RMF, any thoughts?)   7/6/10
Hi Neale,
Many thanks for the advice and the links. That is just what I needed, and I do appreciate the help!
<Glad to help. Good luck with this project. Cheers, Neale.>

More re: Goldfish Filtration: Trickle or Canister (RMF, any thoughts?)   7/6/10
<<I do agree with what you've presented Neale... and would add/reinforce that trickle filters tend to "over-drive" nitrification, producing more nitrate than other modes of filtration/gear... And such filters are noisier, create more smell, and take more power to operate. If it were me/mine, I'd continue to operate this new system on the (perhaps larger) Eheim canister filters (which is what I use on my fancy goldfish systems).
Bob Fenner>>
<<<Thanks Bob for your comments here. I'm a bit skeptical about the whole "nitrate factory" thing because I can't see how, why additional nitrogen would get into a filter just because it's one type of filter compared to another. Surely the food you're adding to the system, plus its ambient livestock density, is what determines how much ammonia gets processed by a biological filter?...
>Mmm, chemical reactions are often "driven" to one side of the equation of reactants/products by factors, conditions... like temperature, RedOx state (oxygen concentration in this case)... RMF<   7/7/10
Re: More re: Goldfish Filtration: Trickle or Canister (RMF, any thoughts?)   7/7/10
Thanks Bob,
Yes, have heard this before. Don't believe it, I'm afraid. Until someone shows me where the *extra* nitrogen gets into the water, I can't see how any one type of biological filter can create more nitrate than any other.
<Interesting... that our perceptions differ here. Am wondering now... if I could refer you to some other examples of reaction series that would serve as better illustration. Do you understand that these (nitrification, denitrification) biochemical reactions are reversible? That they can go "forward AND backward?"... That they can be "driven" more to the products (vs. reactants) side of equations? Wet-dry, trickle... and some other types of filters/filtration simply drive the forward reaction of nitrification toward more product (nitrate)...>
I don't disagree that some filters, e.g., live rock, can create anaerobic conditions where denitrification can take place, and so lower nitrate content relative to what a standard, completely aerobic biological filter can do.
<Oh! Yes... a good example of "more" of the reverse reaction series being thus "driven". B>
Cheers, Neale
7/6/10  cont.... But with that said, I do agree with Bob that most freshwater fishkeepers with demanding fish tend towards external canister filters. Like Bob, I use Eheim canisters and find them reliable and -- when spread out across the lifetime of the filter, 20 years in many cases --
extremely good value. I think it's relevant that the Eheim 2217 that you mention you used, and I use too, is the same design my dad used in the mid '80s -- these are filters that work very well and have no serious flaws.
Being able to adjust the taps on the in/outflow hoses can be very useful when you're balancing flow rate against the low water current fancy Goldfish prefer. You haven't mentioned reverse-flow filtration, but I will raise the idea here. Few filtration systems handle the sheer filth produced by large fish like Goldfish as well. They're relatively easy to maintain as well, if a bit fiddly to install (though surely less complicated that trickle filters). Much to think about, anyway. Cheers, Neale.>>>

Re: More re: Goldfish Filtration: Trickle or Canister (RMF, any thoughts?) -- 7/7/10
Hello Bob,
<Dear Neale>
Yes, I do understand the two-way flow of nitrogen in biological filters.
And I can certainly understand that differences in oxygen availability can effect the balance of that flow.
However, my argument would be that even allowing for a certain amount of nitrogen fixation inside an aquarium biological filter, any nitrogen captured from the atmosphere will be a trivially small amount compared to that supplied via the fish food.
If you're feeding your goldfish a handful of pellets that are 40% protein, the quantity of nitrogen in there -- and therefore the nitrate end product of biological filtration -- will VASTLY outweigh the daily nitrogen fixation by, for example, blue-green algae.
<Also agreed>
My gut feeling is that nutrient input control, the use if skimmers to remove proteins/amino acids before they become ammonia, and the denitrification potential of live rock and fast-growing plants easily account for the perceived variations in biological filter "performance".
<And this>
Anyway, all speculation on my part, and not based on anything beyond education!
Cheers, Neale
<I was thinking that we were speculating re how much more NO3 et al nitrate might be "produced", extant in any given fresh, marine setting w/ and w/o trickle filtration in use... B>
Re: More re: Goldfish Filtration: Trickle or Canister (RMF, any thoughts?) -- 7/7/10
We are, I think. And my argument is simply that so long as the biological filter handles the ammonia produced by the fish, so there's zero ammonia and nitrite, there will also be no real variation in nitrate concentration.
<Actually... this does occur. There is real variation in nitrate concentration using overdriven nitrification means>
So I'd choose a filter that best matched my budget, aesthetics, flow rate requirements, etc.
<I do concur here. B>
Cheers, Neale

Re: More re: Goldfish Filtration: Trickle or Canister (now reverse flow UG)   7/6/10
Neale, can you fill me in on reverse flow filtration? I am not familiar with that.
<A reverse-flow undergravel filter uses the outflow from a canister filter to push water into a standard undergravel filter plate. Water rises from that plate through the gravel, and in doing so pushes solid waste into the water column where it is sucked into the canister filter. The result is that the gravel stays much cleaner than in any other type of aquarium because the gravel is constantly being cleaned. The gravel also works as a biological filter, ensuring excellent water quality. The downsides are these: Firstly, undergravel filters can't really be used with plants. The
exceptions are plants without roots, whether attached to bogwood or floating at the surface; either of those types of plants will grow fine.
The second limitation is that the gravel needs to be more or less uniform for best effect. Water flows along the line of least resistance, so if the gravel bed is shallower at one part of the tank, that's where all the water will flow. Obviously, if you dump big rocks on the gravel bed you'll be creating dead spots that won't work as a biological filter. Finally, you need an adapter to connect the outflow from the canister filter to the undergravel filter. Because of the limitations on plants and rocks, reverse-flow undergravel filters aren't widely used now that people like to
create natural-looking aquaria, but they remain good value filters for situations where large rocks and rooted plants aren't going to be used. If your Goldfish are being kept with a few plastic plants (or Java ferns, or floating plants) and some ceramic ornaments, a reverse-flow filter will work just fine. Cheers, Neale.>
Re: More re: Goldfish Filtration: Trickle or Canister, reverse flow UG   7/8/10

Neale, thanks very much for that explanation. I did not know you could do that. Keeping gravel clean in a goldfish tank is a real challenge, so I have stayed away from it--but I actually would like to have it. It seems that if this is set up properly, reverse filtration may be one way to manage it.
<Glad to help. Yes, a reverse-flow undergravel filter is a "tried and trusted" approach to keeping messy fish tanks clean. Well worth researching. Cheers, Neale.>

(fishless) Cycling tank experiencing nitrite fluctuations 7/15/2009
Dear WWM crew,
Hi! I hope you're doing well and thanks for taking the time to read this!
<Happy to help.>
I'm at the tail end of a fishless cycle for a Betta tank that I'm having difficulty finishing up. Nitrite levels have an infuriating habit of lowering to 0.1 ppm in the morning and then spiking back up to around .8 ppm after I add the daily ammonia dose.
<You're adding too much ammonia for the filter to process "in real time"; try adding half as much, and see what happens.>
They'll then go back down to .1 ppm by the next morning until I re-add the ammonia. The ammonia itself takes less than a day to go back down to zero.
This has been going on for a few days and short of considering a bum nitrite test kit, I'd like to ask your opinion of a few tips I've read about to get the cycle moving, but I'm a little too nervous to try out, lest I disturb the cycle.
<If you've been doing this for more than, say, 3 weeks, the tank is probably cycled good enough to add fish. At the very least, stop adding ammonia, and instead add a tiny bit of flake food each day, just as if there was a Betta in the tank. It goes without saying that ammonia is ammonia is ammonia, and the bacteria couldn't care less whether the ammonia comes direct from decaying flake food or via your pet fish. It's all the same to them! If you find 0 ammonia and 0 nitrite after a few days of this protocol, you're good to go.>
But First, some tank specifics are in order!
tank size: 5.5g, planted, cycling, heated (80F) and filtered (whisper HOB filter with a sponge insert on the intake to protect delicate Betta fins and a baffle on the outtake to reduce the current)
set-up: half an inch of gravel, planted with 2 Anubias nanas, 1 Anubias barteri, 5 bunches of java fern, Christmas tree moss, duckweed a Cladophora ball and a few pieces of driftwood for cover
water additives: Nutrafin aqua plus water conditioner(10ml), blackwater extract (5ml) and weekly Seachem flourish and excel doses(.5ml) for the plants along with tetra Florapride which is added each month (5ml). I'm also adding 12 drops of ammonia each day and Seachem stability was added the first week of the cycle.
water parameters:
ph: 7.6
GH: 120 ppm (this value tends to fluctuate a bit)
KH: 60 ppm
ammonia: 0 (it goes up to around .5 ppm when I add ammonia and goes back to 0 ppm in less than a day)
nitrite: .1 ppm but then goes up to around .8 ppm very quickly after ammonia is added and then back down to .1 by the next morning
nitrate: between 50-110 ppm
uninvited guests: pond snails, Planaria, copepods, nematodes and what I think are Ostracods
<All harmless, and in fact likely helping the cycling process in their way.>
I had left the tank alone until July 8th when I did a partial water change because of a second nitrite spike that brought levels from .3 ppm back up to 1.6 ppm which I attributed to a sudden KH drop. In response to the nitrite levels, I thought the ammonia was inhibiting their growth in some way, so I've been reluctantly lowering the amount of ammonia I add from 20 to 18 then to 12 and finally to 10 drops.
I was dosing 20 drops at the beginning, then 18 when I started getting nitrites, followed by 12 when I had a second nitrite spike and right now I'm adding 10 drops.
I've never found any information that matches my current predicament so I'm hesitant to try some of the cycle troubleshooting advice I've read. They range from water changes, varying the amount of ammonia I add to the very ominous-sounding not adding any ammonia at all for a day or two.
I have to say I'm mildly tempted to skip a day of ammonia, since the nitrites are on the brink of disappearing and adding ammonia is what appears to be keeping them from doing so. But then again, I don't want to have a die-back of the other bacteria. I'm also nervous about adding a fish now, because the gradual lowering of the ammonia dose has no doubt reduced the bacterial bed, no? The bacteria can consume .5 ppm of ammonia in less than a day, do you think that sounds like a ballpark range of waste produced by a Betta each day?
<Who knows? Not a huge fan of using ammonia for precisely this problem; should I need to cycle a tank without fish, I tend to use flake food or bits of seafood to mimic the amount of food added to the aquarium once the first batch of fish are added; this way, I know the filter is getting "used" to exactly the right amount of waste.>
In a nutshell, have you ever encountered this sort of thing? If so, is there anything I can do, or is this another one of cycling's many 'sit down, shut up wait' tests?
thanks for all your help,
<Cheers, Neale.>

Re: (fishless) Cycling tank experiencing nitrite fluctuations -- 07/17/09
Dear Neale,
Thanks so much for the quick response (I can't say so much for myself)! I Just wanted to say that the nitrites finally reached zero yesterday,
and after a large water change I purchased a Betta (who's bag water had a 1 ppm ammonia reading no less)!
Despite that he's got immaculate fins and vibrant colour. He's still a little skittish and his gills might be compromised by the polluted water he was in, but hopefully he'll take a shine to his new surroundings and live out his days comfortably!
<I hope so too. Good luck!>
Thanks so much for taking the time to send me all that information and I'll put it to good use should I ever convince my parents to let me get another tank!
<Sounds like you're enjoying this hobby, which is good news for the future.>
gratefully, Emilie
<You're welcome, Neale.>

Re: (fishless) Cycling tank experiencing nitrite fluctuations   7/26/09
Dear Neale,
(don't worry, I'll leave you guys alone after this message)
<You're always welcome to write!>
It's been about a week since I got my Betta and things are going wonderfully! I can't express how pleased I am!
<It's a lovely aquarium too! It would be a real blessing upon the world if everyone kept their Bettas in tanks as well constructed as this one. Your choice of plants is excellent and should do well even under moderate lighting levels. One thing I'd add though, if you find algae becoming a problem, is add some Indian Fern (Ceratopteris). This floating plant provides shade and cover at the top -- Bettas love the stuff! -- but even better, it's a great algae-buster. Anubias in particular doesn't like direct light, and the edges of its leaves often become covered with hair algae. Floating plants moderate the light a bit, and helps Anubias and other shade-loving plants keep algae-free. Simply crop back the Indian Fern regularly to prevent the tank being totally overwhelmed.>
It's so rewarding to wake up and get to see a healthy, active fish going about his business. In light of this I need to thank you and the rest of the crew for creating this site and for all your patience and advice. WWM is by far the best resource for fishkeepers I've come across and I can spend hours at a time looking through all the FAQs (although I usually skip the Betta FAQs because it depresses me a little) and learn some thing new.
<Ah, yes, the Betta FAQ does tend to be unusually rich in the "same old problems", in part (unfortunately) because pet store clerks seem to continue selling inappropriate Betta habitats, and offer little in the way of useful advice.>
In that spirit, I thought you might like to see a photo of my Betta's tank (I hope it got through!). Most of the final setup is a result of reading your site's articles and FAQs and I thought you'd like to see the results of applying your site's (and enviable knowledge) indispensable resources.
<Thank you for this photo!>
Anyway, I think it's really important that I take the time to let you (and the rest of the gang) know that I recognize and highly value the time and effort you (all) put into WWM because I'm often disturbed by how ungrateful some of the people who write in are. Once again, eternal thanks and I hope I accumulate enough experience to become as knowledgeable as you all are!
<And thank you for taking the time to write! Good luck with your fish, Neale.>

Strange rise in nitrites, FW, goldfish ongoing...   7/11/07 Hi Bob/whoever's got this! <Just me, Neale.> Just a couple of quick questions today, if you please - I've been treating my fantail (Horatio) on Neale's advice using Interpet Aquarium Treatment No. 8 (Anti Fungus and Finrot, active ingredient phenoxyethanol). I started the treatment three days ago and I'm delighted to say that it's made all the difference; kindly thank Neale very much for his advice as my fish is no longer ill and is perky and happy as he used to be! <Very good.> I have been regularly testing his water parameters and they have consistently been pH 7.5 (approx), ammonia 0, nitrite 0, nitrate <5mg/l. However, this evening I tested his water and the nitrites, while not actually showing dangerous amounts per se, have risen so as to be detectable (though still less than 0.1mg/l). Naturally I am concerned and loathe to take immediate action as I don't want to remove the medication from the tank (there are four days of the seven left to go before I can change the water). My questions are as follows; <Odd. Most modern medications have no effect on the filter bacteria. I'd tend not to worry too much, but test for the next couple of days to see if this is a blip or a developing problem.> 1) What could be the cause of this peculiar rise in nitrites? Since I've been testing Horatio's water (going on two months now) the results have been steady. I've never had any ammonia or nitrites present, and nitrates have rarely risen above 5mg/l. The only recent difference is that I've started using dechlorinator (Interpet Fresh Start), and there is a question saved on WWM that states that this product can increase levels of nitrite - could this be relevant? Horatio is (as you may remember, Bob, having spoken to my girlfriend Sarah previously about this fish) living in a far-too-small tank (11 UK gallons) at the moment, so I have been carrying out extensive water changes - almost daily - to prevent build-up of unpleasant water elements until the new tank is cycled and ready for him. However, because on Saturday night I added this medication, I haven't changed the water for three days. Could this be the cause of the nitrite rise? <Most dechlorinators break down chloramine (which we want them to do) into ammonia and chlorine. But not all dechlorinators will "mop up" that ammonia. If your filter is too small, then that ammonia could be being processed into nitrite relatively slowly, giving you the nitrite reading you're observing. Either way, it's important to establish if your water supplier uses chloramine or not. If they do, get a dechlorinator that removes ammonia.> 2) What do I do about it? Should I keep watch on the situation and see if the nitrites remain at a vaguely "acceptable" level/diminish (is this level even safe?)? Or should I change some of the water to dilute the nitrites, as I would automatically do if not for the meds - and if I do, is it safe to proportionally add some more medicine or should I leave it and take the risk of Horatio not being properly medicated, leaving the possibility of having to treat him again within a short space of time (obviously not desirable)? <For now, your priority is to stick to the instructions for the medication, avoiding water changes. But once you've finished the course of medication, do the water changes and check the filter is working properly. It may need a bit of a clean to rinse off detritus. Follow the instructions that came with your filter, paying particular attention to keeping the bacteria on the sponges happy (i.e., don't rinse the sponges under the tap, but bathe them in a bucket of aquarium water). Doing water changes midway through a course of medication is a bad idea if you're told by the instructions otherwise. The problem is the medication decays over time, to "topping up" with an extra dose is likely to screw up the concentrations.> Okay, maybe that wasn't as quick as I'd hoped. Thank you once again for your patience and for your immensely helpful site and staff; you have been terrific to us over the last few months and I'm sure Horatio appreciates it! <Good luck!> Oliver <Cheers, Neale>

Re: Strange rise in nitrites (FAO Neale)  7/11/07 Hi Neale, Don't worry, I haven't any more problems (well, at the moment!); just wanted to write back and thank you very much again for your prompt and informative response. I'll do exactly as you said. Not sure what I'd do without WWM! Hope you're having a good day and you've got better weather than me here in Glasgow :-) Thanks again, Oliver <Cool. And no, the weather here is pretty clarty as well. Good luck! Neale>

Bridge decoration causing high NO2?  - 4/6/07 Hello! <Hello.> Could the bridge decoration in my 10 gallon tank be causing high levels of NO2? <If it is specifically designed for use in an aquarium, the answer is no. If some nick-knack you picked up from a gift shop on holiday, who knows?> My water readings today at the LFS were pH=7.0, NH3=0, NO2=2.0, NO3=60ppm, and PO4= 0.25. <The nitrites (NO2) are too high -- long term, that's going to harm your fish.> The LFS suggested that sometimes the decorations can be the culprit, especially things such as castles or bridges that are often painted. <Never heard that before. Sounds very unlikely. Nitrite comes from ammonia, ammonia comes from decaying nitrogenous compounds such as protein, and protein comes from fish food, dead animals and plants in the tank, etc.> The tank is about 6-7 weeks old and currently has 3 Platies and 1 Corydoras. <OK, the nitrite is probably because the filter is immature and/or you are feeding the fish too much and/or the filter is too small.> The bridge was bought from PetSmart and was sold as an aquarium decoration so I assumed it would be safe. The bridge has been in the tank since I bought it. <Simple solution: take the bridge out. If things get better, then leave it out. If nothing happens, it isn't the bridge.> About 3 weeks ago, all of the readings were good according to the LFS and I added 3 guppies. They have since passed away. They looked good for 1-2 weeks and then I lost all of them individually over a period of a week or so. The symptoms were stopped eating, not swimming around much, dead when I got home from work. <Almost CERTAINLY an immature filter/overfeeding/too-small filter. Guppies are quite delicate, and will die in poor water conditions. Wild guppies are very hardy, but fancy guppies are not.> The Platies and Corydoras are active, eating, and seem to be doing OK although I know the high NO2 is hurting them :-( <Good that you know, so now put that into action by [a] not buying any more fish so the filter can mature; [b] reducing the amount of food you give the fish by 50%; [c] doubling the number of water changes, or at least doing a 50% water change twice a week until the nitrites drop to ZERO; and [d] checking if the filter is big enough for your aquarium. Your thoughts on the cause of the high NO2? <See above.> Thank you so much and thank you for your wonderful website! Michele <No problems. Good luck! Neale>

Nitrite And Ammonia Problems In A Big Tank   12/21/06 I adopted a 150 tall FW tank with a sand bed, two bio-wheel filters, one canister filter, several pieces of driftwood. Living in it our 4 grown Severums, 2 grown Jurupari, 1 2.5ft fire eel, 3 African clawed frogs, 1 small Knifefish, 1 Pleco, and 2 3 to 4 inch eels. I have had it running for about 3 months.  It seemed to cycle the first week I had it (even though we moved it entirely and saved all the media)  - with nitrites and ammonia levels going to 0 after numerous days of massive water changes My problem is that about every 10 days the nitrites and ammonia test heavy again. I repeat several days of massive water changes and it returns to a clean state. But without fail about 10 days later it goes off the charts. A local fish guy suggested that the sand bed is responsible. I took about 1/2 the sand out - from 3 inches to about 1.5. but it did not stay clean. I have also put ammonia rocks into all the filters - but they have never "turned green" which I was told means my ammonia test kit is giving me a false positive. I am willing to replace the sand with gravel and even install UGF is necessary - both ideas have been suggested. I do not overfeed. There are no dead fish. There is ample biological media in both wheels and in added media in all filters. Any ideas? Does sand in a FW present problems. I have 12 other tanks and everyone is cycled and stays that way. Thanks Tim < Do a 50% water change, vacuum the gravel and clean all the filters. Chemical waste levels should be down to zero. Feed as you normally do and test the water daily. I think you will find a logarithmic but gradual increase in these levels over a few days before they peak. The Bio-Wheels are great little inventions and you are correct that they should be handling all the bioload for this tank. The problem is in the canister filter. Food/waste gets trapped in the canister filter and there is very little oxygen in the canister for the bacteria to live on and break down the waste. So now the fish are generating biological waste and so is the crap in canister filter. The outflow of the canister filter has no measurable oxygen so bacteria cannot live and break down the waste. I would recommend that you add a bio wheel attachment to the canister filter outflow before it goes back into the tank and that you vacuum the gravel every time you do a water change. If the driftwood is not suitable for the aquarium then it could be rotting and contributing to the problem.-Chuck>

Tap water nitrites off the charts!  02/12/06 Guys, Just out of curiosity I checked my tap water for nitrites... It was nearly the max of my test kit. What is up with that? <Trouble... either a faulty test kit (hopefully) or dangerously toxic source water (even for you)> Isn't it spiking the heck out of my water when I add it to my tank? I did a water change three days ago, and my in-tank readings are normal today (zero ppm for nitrites), but is the initial addition of the water dangerous to the fish? <Yes, can be> I change about 20 percent weekly... Thanks <I would first "check your checker"... with another test source. Get/use an RO device for your potable uses... Bob Fenner>

Persistent High Nitrite Level FW  1/31/06 I have read other messages on your site and other articles on other sites about high nitrite levels, but I still don't quite get it. I have a 10 gallon tank with 10 fish: 2 balloon belly mollies 2 ghost catfish 5 orange von Rio tetras 1 algae eater There are many, many small snails that were acquired accidentally with an aquatic plant that died some time ago. . . The snails, however, live on and reproduce at a staggering rate. <Mmm, you might want to collect and remove a bunch of these periodically... easy to draw to a small glass tray with a sinking bit of algae based food or blanched vegetable... as bait> Until today, I had a philodendron sticking out the top of the tank with its roots submerged. I took it out thinking that this was perhaps contributing to the problem. <Oh! Yes> About a week ago one of my mollies (there were three) started to act strangely as if she couldn't submerge. She would still eat when given food, but couldn't swim down to eat off the bottom like she always had. She had also lost a lot of weight. Eventually, she became very lethargic and got to the point where she was upside down and couldn't turn over. I took her and another sample of tank water to the local pet store. They said it didn't look like she had any disease and offered no explanation as to her condition. I assumed it was just old age and I only include this description in case it is symptomatic of some other problem. Anyway, when the girl at the store tested the water (something I had never done--shame on me), she said that the pH level was low and that I should increase it with a pH increaser. I bought the pH increaser and a test kit that tests for NO3, NO2, GH, KH, and pH. When I got home, I did a 30% water change and added 1 tsp of salt, which is my normal routine. (I keep around 3 tsp of salt in the water at all times.) I did not add any pH increaser. I tested the water immediately afterward and it looked OK except the water was hard, so I added a teaspoon of salt. The next day, however, the levels were as follows: NO3 = 40 <I'd keep this under 20 ppm> NO2 = 1.0 <Dangerous... should be zip, nada, zilch> GH = 300 KH = 0 pH = 6.8 I added another teaspoon of salt and changed the filter which was very dirty (because I had made the water very silty the last time I changed it--explanation below). The next day, the nitrite level was at 3.0. <Yeeikes!> I did another 30% change and waited an hour before testing. The nitrite had gone down to 1.0. One day later, it was back up to 3.0. The next day, 3.0 again. The following day, 5.0. Today, it was still 5.0 so I did another 30% water change. One hour later, the levels are as follows: NO3 = 40 NO2 = 3.0 GH = 150 KH = 40 pH = 7.2 There is currently about 8 teaspoons of salt in the water. <Mmm, you might want to mix some of this salt up in tapwater and test it for nitrite...> The strange thing (to me) is that the fish seem to be happy and healthy. From everything I have read in the past few days, a 5.0 nitrite level should have them dropping like flies! <Let's see... luckily your pH is low... if it were a little higher, the nitrite would be MUCH more toxic> I have checked for brown coloring of the gills and see none. They are not gasping for air at the top of the tank either. I can only surmise from what I have read that the salt is keeping the nitrite from being as toxic as it otherwise could be. <Oh, yes... this also> I have noticed the mollies scraping themselves occasionally on a structure in the tank. I read today that this was one sign of nitrite poisoning. I have had this tank for 8 months now and only three fish have died in that time (except for the batch I introduced right at the beginning before the tank had cycled!). About a month ago, I did a very thorough cleaning of the tank. I really stirred up the waste on the bottom, trying to get as much out as possible. I took out all the structures and washed them with hot (not soapy) water. I changed the filter as well. I also started feeding them much more around that time. Basically, I unwittingly did everything I could to raise the nitrite level! My questions are this: 1. Why isn't the level decreasing? <I suspect the houseplant> 2. Why are the fish still alive and acting normal? <They're tough, adapted to it, and the salt> 3. I have read on some sites of a biological filter or a biofilter: Is this (a) just another name for the normal filter, <Mmm, of a sort... all filters are ultimately biological to degrees> (b) a different kind of filter that I should have, or (c) just a term that refers to the nitrogen cycle that occurs within the tank? <Mostly the latter> 4. Could the snails be causing problems? <Yes... carry disease... and can influence water quality in high numbers> 5. I have read that most of the bacteria live on the filter. Wouldn't changing the filter then lead to these levels getting all out of whack every time? <Yes... a common problem/occurrence. In established systems not such an issue> Thank you for any help you can provide. - Bryan <I would read over WWM re FW filtration, add more filtration, remove the houseplant, reduce the number of snails, test the salt... Bob Fenner> Re: Persistent High Nitrite Level... Betta systems and snail removal technique  2/3/06 Thank you. After removing the philodendron, the nitrite levels immediately dropped and are now < 0.5 ppm. Other levels are beginning to even out as well. <Ah, good> I thought you also might like to know that I have rigged up a plastic fork on some fishing line as a snail remover. I stick a piece of vegetable on the tines of the fork, and when a few snails crawl on, I hoist it up and scrape them off. It's not pretty, but it's been fairly effective! <Neat! Bob Fenner>

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