# nitrates staying at 20ppm



## sevmeera (Aug 8, 2009)

Hi guys, I have a 72g tank with peacocks and small haps, ranging in size from 3"-5", I do weekly 30% water changes, vacuum the substrate with each change, no nitrates in the tap water, I clean my filter (Fluval fx-5) once a month religiously, yet after every water change the nitrates still test at 20ppm. I don't understand it, I changes the hoses on the fx-5 thinking maybe waste was collecting in between the ribs in the ribbed in take and outlet tubing, I scrub the baskets inside the filter, clean sponges etc. The only thing I thought of were perhaps the bio-media is holding and leaching nitrates back into the water? The bio seems fairly clean, just a small coating of brown which I thought was bacteria. Or maybe the decay of brown algae on the rocks is causing it? Can the sand substrate hold in nitrates? Any advice would be greatly appreciated, as I have run out of ideas..... :-?


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## Bweb (Mar 31, 2009)

Could be an old test kit do you us strips or liquid with test tubes even if you just bought it it could have sat on the self at the store for a long period the test strips are not that accurate. Is their a dead fish behind some of your tanks decour. How many fish are in the tank how big are they an FX5 for a 72gal. should be more than enough filtration. Try bigger water changes Probably a bad test kit are your fish dying if not your probably fine.

I hardly ever test my tanks I do 50% WWC and when I do test them they are spot on and I have 15 good size tanks.


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## fox (Jun 11, 2009)

What does the water test at before the WC?


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## sevmeera (Aug 8, 2009)

Thanks for the responses,no dead fish lol, just re-did the rockwork. I have 12 fish total, with the average size being in the 4-4.5" range. The water seems to test somewhere between 20 and 40ppm before the water change ( I have trouble telling the difference between 20 and 40 sometimes).


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## Darkside (Feb 6, 2008)

Get a new test kit or have a LFS test it independently for you and compare the results. Test kits have a limited shelf life.


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## fox (Jun 11, 2009)

Well that sounds about right , 20 - 40 ppm before 30%WC, ~20 ppm after. You might have a stale test kit but I am thinking it is giving acceptable results from doing the math. i.e. it might be 35 ppm b4 and ~20 after doing a 30% WC.

Mebbe do a bit larger WC say 40 - 50% once a week or do a gravel vac once or twice mid week of ten gals or less.


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## 3kgtchic (Apr 16, 2010)

You had some good questions that I too have... I hope more people respond. :thumb:


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## Bweb (Mar 31, 2009)

Just another thought I only clean the front and side glass in my tanks and let algae grow on the back wall and rocks in my tanks. My theory is that the algae may help in keeping the nitrate levels down.

0.02


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## sevmeera (Aug 8, 2009)

I wondered that too, but then I also wondered if algae was similar to skin that is constantly dying off, and whether the decay of older algae may affect nitrates, pure speculation of course, I was never good in science class lol. :lol: This my sound off-the subject, but it does have something to do with water changes, I had an idea to make my water changes quicker, first I should say that I was never a fan of adding de-chlor straight into the tank while filling it with a hose, so the following idea is only an idea for people who don't.

I have a 29 gallon tank sitting right next to my 72g tank, I am currently using it as a hospital tank/ quarantine tank. My idea was to empty this tank out completely, clean it, leave the heater, and fill it with water with my python. Then de-chlorinate the water in the 29g, and buy a seperate aqua-stop valve for the fx-5 with some 1" tubing.

This would allow me to detach the intake from the fx-5, and pop on the new one with the 1" tubing. I could then use the fx-5 to pump the water from the 29 into the 72.

This way I could always have water ready, at the right temp, de-chlorinated, and ready to go, no more buckets, ladders, etc. Plus the water would be flowing through the fx-5's diffuser, so no crazy sandstorms would happen. I really think this might work! if so, it will save me a lot of time and back aches. What do you guys think?


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## Chris2500DK (Feb 15, 2006)

Bweb said:


> Just another thought I only clean the front and side glass in my tanks and let algae grow on the back wall and rocks in my tanks. My theory is that the algae may help in keeping the nitrate levels down.
> 
> 0.02


That's not just a theory, algea will reduce nitrates and phosphates when they grow. The problem is that unless you manually remove the algae in some way, either by scraping it off and taking it out or having algea eating fish eat it and then siphon out the fish poo, the nitrates and phosphates will be released again when the algae dies off.


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## sevmeera (Aug 8, 2009)

all I have is brown algae, which isn't really algae at all, but diatoms, will these help reduce nitrates and phosphates as well? or is it just green algae, hair algae, etc. that does this?


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## Chris2500DK (Feb 15, 2006)

Brown algae is usually caused by silicates and nitrates. They mostly appear during tank startup and are most often replaced (outgrown) by green algae.

Your nitrate level could be kept up by the decaying brown algae, but that should usually pass if you're doing good waterchanges and it sounds like you are.

Have you tested your tap water? If your tap water has 20 ppm nitrates you're not going to get below that with water changes 

How much light do you keep on the tank?


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## sevmeera (Aug 8, 2009)

Thanks for the replies! I have tested the nitrates from the tap before, although not lately, and there were none, I will test again to make sure. I have a coralife 10k, and blue actinic combo, that I leave on for 9-10 hours per day, starting at 11:30am and turning off around 9:30 at night, this schedule has slowed the growth of brown algae, but it still comes back by the end of the week when I clean it off during the water change. the only spot I don't clean regularly is the rocks, because it is such a pain in the a$$!


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## Chris2500DK (Feb 15, 2006)

What kind of rocks do you use? If they're leeching silicates slowly that might be the cause of your problems.


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## sevmeera (Aug 8, 2009)

I use all lace rock in that tank, I thought it was chemically inert, but I may be mistaken.


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## Rhinox (Sep 10, 2009)

fox gave you the best advice, but you seemed to ignore his post. Its all about the water changes. You haven't said what test kit you're using, but with the API liquid test kit, once you get to 20ppm nitrate and above, all the colors sort of run together and its pretty much impossible to have an accurate reading. What you're reading as 20 may even actually be twice as much or more and you might not be able to tell the difference.

Now, the math is pretty simple. If you test your nitrates before, and you know the percentage of water you're changing, and there is 0 nitrate in your tap, all you do is multiple the before level of nitrates by 1 minus the water change percent and you'll get your after nitrate level. So, suppose you measure 40ppm before, and you do a 30% water change, 40 times 1 minus 0.3 equals 40*0.7 equals 28ppm - so obviously you're not going to get a reading below 20.

Now, here's another bit of math. I suppose an average value of weekly nitrate production for a tank is 10ppm per week. If you only do 30% water changes, over a long time when the nitrate becomes stable, the math works out that at the end of the week just before the water change, your nitrate level will be 33 1/3ppm. Then, you remove 30% of that with a water change which drops you down to 23 1/3ppm, and then at the end of the next week, you're right back up to 33 1/3ppm again. So, unless you're stocked lighter than 10ppm nitrate production per week, you'll never have nitrate levels under 20ppm with consistent 30% water changes. You need to change more water.

On the other hand, suppose your tank is producing 10ppm nitrate per week. The math works out that with 50% weekly water changes, your nitrate level at the end of the week will be 20ppm, and drop to 10ppm immediately after a water change.

Here's another test. If you think your nitrate is 20ppm, do a 50% water change. If your test kit doesn't give you a reading of 10ppm, its either a bad test kit, or you had more than 20ppm. Keep doing daily water changes until you get down to a more readable level, and then try to get a good estimate of how much nitrate your tank produces in a week. Once you know your tanks weekly nitrate production, you can determine how much water you need to change to keep the value under whatever level you want, and you can also make a pretty good guess as to whether you need to be looking for an alternate nitrate source besides your fish. Based on you do 30% water changes, even if you had a reasonable nitrate production of 10ppm per week, you shouldn't expect to have less than 20ppm nitrate ever, so I'd start with 50% daily water changes until you can read a nitrate level of 5ppm, then wait 1 week and measure again. If it looks like 10-20, your nitrate production is normal and you need 50% weekly water changes. If it looks like 20ppm or more, you have to decide if its because you're waaaay overstocked, or if you have a nitrate factory somewhere (trapped detritus or overfeeding). But nitrate doesn't come from no where, and there is no magic to making it disappear either. Change more water and you nitrate will drop.


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## sevmeera (Aug 8, 2009)

Thanks for the response Rhinox, part of the question I had was about the nitrates staying at 20ppm, and if I were someone just starting out, without the knowledge of the nitrogen cycle then your answer would have been absolutely perfect, however, I have had the same amount of fish in this particular tank for many months, and have only been noticing the higher levels of nitrates over the last month or two, as I mentioned before in a previous post, I have done everything short of emptying the tank to try and find the source.

Thus I was asking the other questions, can brown algae decay produce nitrates, does the bio media hold enough nitrates to leach back into the water, etc....

I asked those particular questions to try and cover all the bases and see if anyone out there had any possible feedback as to other possible sources of nitrate in an aquarium, and because it was a topic that I was curious about, one of the many vagaries in aquaria that don't seem to be asked about much.

I am starting to think it may just be a faulty test kit, which is disconcerting because it was "new", but in light of all of the other evidence, it seems to be the logical explanation, I am going to purchase an additional test kit from another manufacturer tonight and test again, I hate to do it with the cost of test kits and the fact I just bought one recently, but what can you do.

I will post the results as soon as I can ( if you care , lol) and post them. Thanks again for the replies!


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## kmuda (Nov 27, 2009)

Any organics (or proteins) added to the water (or in the water) will wind up as Nitrate. Food, Fish poo, dead bacteria, plant leaves, uneaten food, etc.......

So to answer your question.... absolutely, old biomedia can become nitrate factories, of a sort. Being someone that attempts to manage nitrates down to zero.... and being someone who has tested a minimum of 4 tanks daily (for nitrate) for several years, I can pretty much attest to the causes of nitrate and what does... and does not... result in lower nitrate creep. It's somewhat of a hobby within the hobby for me.

One of my "best practices" is regular recyling of my biomedia. Each month, about 1/3 of the media is pulled from my canister filters and replaced with recyled media. The media that is removed is rinsed in a sink (using one of those dish sprayer attachments), then it is boiled for a least 1/2 hour (sometimes longer), then it is returned to the sink, rerinsed, then dried for reuse. For especially dirty biomedia, I also use a product called APPlus Plastic Plant cleaner, soaking in a solution of this stuff (same strength used to soak plastic plants) overnight, making sure to rinse the bejesus out of it before reuse.

This process has several purposes. Primary is that it keeps the internal pores of the media clear. Quality media will support a small measure of denitrification within it's internal pores (some more than others.... best results have been with Hagen -not Fluval - BioMax and SeaChem Matrix). But as bacteria die, these pores fill with bacteria, and you loose the denitrification capacity of the media. In addition, those dead bacteria become a food source for heterotrophic bacteria, boosting their quantities, which results in layers upon layers of bacteria corpses on the surface of the media, being feed upon by subsequent layers of living heterotrophic bacteria, all of which eventually becomes nitrate. Not to mention, you want those pores open for autotrophic nitrifying bacteria (and the internal pores open for denitrifying bacteria) and as the pores fill in and the surface of the media becomes caked with heterotrophic bacteria, the overall surface area is reduced, and you wind up with less area for the nitrifying bacteria to colonize.

The boiling, specifically, serves two purposes. Heterotrophic bacteria can survive the rinsing and it can even form spores that can survive being dried out. Boiling eliminates ALL bacteria living on the media while "boiling out" their corpses. Just rinsing, even if it kills the bacteria, will leave the corpses behind, to be consumed by additional bacteria.

None of my canister filters goes beyond a month without cleaning...... with a similiar process occuring with the various sponges and sort within the canisters. I also run a strong HOB on each tank specifically geared towards mechanical filtration, with this mechanical media undergoing a similiar process on a weekly bases (it's replaced with new or recycled mechanical media), with the removed media being boiled (boiling will return blue bonded padding to a "like new" condition, fluff and all).

Granted, I'm a bit of a tank cleaning freak (understatement :lol: ), and my approach is the opposite of effortless, but it does achieve results. Follow this process, and before long, your closets and drawers start to fill up with stuff.


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## Rhinox (Sep 10, 2009)

> however, I have had the same amount of fish in this particular tank for many months, and have only been noticing the higher levels of nitrates over the last month or two, as I mentioned before in a previous post, I have done everything short of emptying the tank to try and find the source.


I have a 30g tank with 24 1" to 1.5" mbuna in it. I estimate that the tank produces around 10ppm nitrate per week. My 55g tank with 6 labs, 6 aceis, and 5 lucipinnis produces about the same. Lets say I started out with 0 nitrate and did 30% water changes. The nitrate would go like this:

Day 1: 0ppm
Day7: 10ppm before water change, 7ppm after
Day 14: 17ppm before water change, 12ppm after
Day 21: 22ppm before water change, 15ppm after
Day 28: 25ppm before water change, 18ppm after
Day 35: 28ppm before water change, 19ppm after
Day 42: 29ppm before water change, 21ppm after
---so, after a month and a half, it would appear that nitrates would not drop below 20. And that should be expected if all you're doing is 30% water changes, and had a very reasonable normal tank nitrate production of 10ppm per week. So what I'm trying to say is, there is not reason to tear the tank apart, or blame it on a faulty test kit or brown algae or anything, because the math says if you have an average weekly nitrate production due to the fish and you're only going to do 30% water changes, you're not going to ever have below 20ppm nitrate.

I understand that does not fit your situation perfectly, but it is just one hypothetical example. Smaller fish produce less nitrate, large fish produce more nitrate through more respiration and more feeding, so as fish grow, nitrate production increases 2 fold. You are looking for a nitrate source that isn't there I'm afraid - if you want to know if there is an extra nitrate source, you need to get your nitrate down to a level where you can measure the weekly nitrate production, and the way to do that is through water changes - more than 30%.


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## kmuda (Nov 27, 2009)

Rhinox said:


> if you want to know if there is an extra nitrate source, you need to get your nitrate down to a level where you can measure the weekly nitrate production, and the way to do that is through water changes - more than 30%.


Absolutely, I failed to mention I reset my nitrates to zero, each week, on each tank. Makes it easy to determine your true measure of nitrate creep. But then again, I am dealing with South Americans, not Africans, so I am not doctoring my water to alter chemistry.

Also... I throw the nitrate test kit "results cards" out the window and follow a simple approach.

Yellow = Great
Orange = Good
Red = Bad

And that goes with those cross colors. Any shading of red is bad, even if the overall results are orangish. The more red it gets, the worse it is. Test enough, with low enough nitrates, and you know what I mean.


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## sevmeera (Aug 8, 2009)

Thanks for the responses guys! very good advice, very sound practices, I am happy to say though that I tested the tank tonight with a new test kit (still API, couldn't find anything else) and the nitrates seem to be just above ten, I performed a water change last Saturday ( 30%), so I think it was definitely the test kit (not going to buy them at that place anymore). I am very relieved and feel much better about my cleaning regimen. :dancing:

I totally agree 100% with everything you guys said, and everyone that keeps fish would do well to follow your example.

The only reason I was resistant to the idea of the nitrates building in such a manner as you put forth was that I had seen very stable results on a weekly basis, 15-20ppm at the end of the week, 5-10ppm after water change, consistently for months, I feel silly that I didn't get a "new" tester sooner, I guess being cheap isn't always a good thing! :lol:

Thanks again for all of the great advice, even if it wasn't the particular case here, it is great information nonetheless and would make great reading for someone who needs to figure out a maintenance plan.


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## Chris2500DK (Feb 15, 2006)

Good to hear you figured it out


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## Heyguy74 (Aug 11, 2005)

Large water changes or twice weekly water changes will reduce your Nitrates.


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