RSS Facebook Twitter YouTube




Nitrate levels up..

Home Forums My Aquarium Nitrate levels up..

Viewing 8 posts - 1 through 8 (of 8 total)
  • Author
  • #303684


    I’ve just done my weekly water test and all my levels are stable and within normal range The only one I’m slightly concerned about is Nitrate which has gone up from 5ppm to 10ppm (or somewhere in the middle – the colour is just a bit darker than 5 according to the chart read in broad daylight.  Having researched possible causes the only thing I can possibly pin it to is over feeding, despite only putting in very small amounts at a time and scooping out the excess as best I can.  It’s a 65 litre tank I’m feeding them Tetra Pro Menu crisps.   I’m due to do a water change on Monday but I’m wondering if I should do it sooner or if 5ppm increase in a week is not a big worry.   The fish themselves seen spritely and are feeding well and have good colours.



    Nitrates will naturally raise over time as ammonia is transformed to nitrites and nitrites are transformed to nitrate by bacteria in standard biofilter.

    The nitrates are the end of this aerobic degradation pathway so they pile up.

    Usually they are removed by water changes (which will also remove any other accumulating things that might also be accumulating from bacterial or fish metabolism).

    Alternatively, they can be reduced with more complex filtration systems that either have a anaerobic filter environment of additional unusual filter substrates (housed in a separate filter). These approaches favor bacteria that remove oxygen from the nitrates. This can lead to the generation of nitrogen gas (which diffuses out of the water) and the decrease of nitrates.

    This can also go on in little nitches in your aquarium that have low oxygen levels, such as in gravel where there is not a lot of water circulation.

    Of course the more food you throw, in the more nitrogen, (in the form of ammonia, nitrites, and nitrates you water system will have to deal with.

    You could also use a chemical filtration media to remove the offending compound(s). This would either require periodic money and labor for media replacement or labor for media regeneration.

    Personally, I would just change the water until you get your nitrates to your desired level.


    Byron Hosking

    I agree with what Bill has posted, and that is a good explanation too.

    I am in the group that believes nitrates should always be as low as reasonably possible, given the setup (every aquarium has biological variations), and my tanks generally run in the 0 to 5ppm or a couple in the 5ppm to 10ppm range.  I do stock somewhat heavily, and I have live plants.  Water changes of 50-60% every week without fail, including a vacuum into the substrate in a couple tanks (won’t go into the difference).




    Hello Bill and Byron,

    Thank you for your replies and advice.  I’m sorry I haven’t replied sooner, I was having a heck of a job logging in.

    My Nitrate levels have remained steady at 5ppm, so I think I may have been too quick to panic.  My fish are happy and healthy and eating well (I always just give them small amounts at a time and scoop out any excess) so that’s good.  I always vacuum the bottom of my tank when we do a water change.

    I’m just wondering what effect plants could have because in my Naivety I bought quite a few Amazon Sword in the beginning, not realising they were absolute triffids that would take over my tank!! I think I need to rethink the background plants… hah



    I’m still on top of my regular water changes (including removal of any detritus from the gravel and checking my filter, rinsing sponges and medium in tank water as necessary) and removing dead plant matter as it occurs, but my nitrate levels aren’t going below 5ppm.  My fish are very healthy and eating well and the booklet of API liquid test kit I use says anything under 40ppm is considered normal.

    Am I worrying too much?



    I wish everyone maintained their fish at such low levels. I often joke that when I started fishkeeping, Nitrate wasn’t even discussed as an issue for freshwater, yet my fish grew and were healthy. Seemed that it only started to be a problem once we read about it…
    I would be extremely happy with those test results, so don’t worry about it, let your fish tell you if you’re doing it right. Keeping fish is as much art as it is science, but it is meant to be a pleasure. There was a period where I was testing each day, pH, dissolved oxygen, Nitrate, and fretting if any of them varied from what exactly what I wanted. The fish were probably stressed far more by my tinkering than if I’d relaxed, watched them and missed a water change every now and then.


    Byron Hosking

    I agree that nitrate is something being considered more now than it used to be.  There are several areas where long-held thinking has been challenged and frankly found to be lacking substance.  Nitrates is one of these.  But before I explain, I do not believe you have anything to worry about with nitrate at 5 ppm, or even 10 ppm, provided it is consistent over time as it should be in a balanced aquarium that receives adequate water changes.

    The number of 40 ppm nitrate used to be bandied about, but this is in fact too high.  Dr. Neale Monks has frequently written that nitrates should always be kept below 20 ppm.  The problem is not immediate but accumulates over time, and there seems evidence that some species are more affected than others.

    Ammonia, nitrite and nitrate are all toxic to fish.  Ammonia and nitrite are more serious in that they act fairly rapidly to deb ilitate fish; even if the fish “survive” poisoning by ammonia or nitrite, there is usually internal damage that can have repercussions down the road.  Nitrate is less obvious, but recent studies have demonstrated that increasing nitrates, or continuing exposure to nitrate, will in time cause trouble for fish, leading to death.  It depends upon the level, the exposure period, and the species.  As Dr. Monks has written, nitrates at 40 ppm can cause severe issues for many fish, including as one example cichlids.  Some sources are now advising high nitrates as a major factor in diseases such as Malawi Bloat that previously was largely blamed on inadequate diet.

    All of this should not be a surprise when we consider that no fish we keep in aquaria are exposed to nitrates much above zero in their habitats, and they have evolved to function best in such environments.  My tanks run at 5 ppm, or at any rate the API liquid test indicates between 0 and 5 ppm, and have done for as long as I’ve tested.  I don’t test much now, except if something seems to be wrong and water testing is one of the first steps we take, but a sudden rise from what has been consistent over a period of months is cause for concern in an established aquarium.




    Thank you so much for putting my mind at rest!  I am glad I’m not the only person who fretted about water test results.  🙂

Viewing 8 posts - 1 through 8 (of 8 total)

You must be logged in to reply to this topic.