High Nitrates and Denitrator

[pbkuhn123]

Hi all, I would like to get some input on climbing nitrArate reading. In my 36 gallon, I have two HOB filters that use carbon filter cartridges. Upon my last two weekly water tests on this tank I have noticed the nitrates have been hovering at least at 40 or higher (I can't really tell the dif between 40 & 80 on the API color chart), and this is AFTER water changes. I found this article on why Nitrates can't ultimately be controlled through water changes unless you change 100% of the water. Of course, the article doesn't NOT devalue the benefit of water changes but seems to make a good point here.

Here it is: Aquarium Information - Water change and nitrates

I do know you can purchase Denitrator media, but since this tank uses and HOB filter I cannot add that media to it.

Would love to hear input on the article and use of denitrator products particularly for HOB filters that use cartridges.

 

[PNWaquarist]

The author of the linked article seems a bit obtuse. Uh, yeah, you're never going to get rid of every nitrate ion in your tank via water changes. But you can get rid of enough of it via water changes that it can be kept in check at healthy levels. If the author had looked closer at his/her own math before writing this article, he/she would've seen that the percent nitrate increase per week decreases by 50% after every water change, and will eventually reach a point where the percent increase of nitrate per week will be negligible. Let's see what happens in subsequent weeks...

Week 5: 9.37 units + 10 units = 19.37 units/2 = 9.69 units

Week 6: 9.69 units + 10 units = 19.69 units/2 = 9.84 units.

Week 7: 9.84 units + 10 units = 19.84 units/2 = 9.92 units

Week 8: 9.92 units + 10 units = 19.96 units/2 = 9.96 units

Week 9: 9.96 units + 10 units = 19.96 units/2 = 9.98 units

Week 10: 9.98 units + 10 units = 19.98 units/2 = 9.99 units

If 10 units of nitrate are produced each week and 50% WCs are done each week, the tank will contain no more than 10 units of nitrate. So, yes, the nitrates are indeed "under control" in that scenario.

After being shown the light by an e-mailer, the author then admits that his/her own calculations prove that no more than 10 units of nitrate will be produced in the hypothetical tank, but then mysteriously proclaims that the math doesn't matter and that the nitrates are still out of control by rationalizing a nonsensical scenario of perpetual 100 ppm nitrates due to the mass of fish food added per week.

Despite what this genius claims, nitrates CAN be kept in check via weekly water changes if you don't let them get out of control. And even if you do, nobody's stopping you from doing several large water changes in a row to knock them back to your desired range.

Outside of doing 20-50% weekly water changes, I'd recommend Hornwort. Because it grows fast, it consumes a lot of nitrates. Buy a few bunches from your LFS and suction them to the top part of your tank with veggie clips. And, of course, don't overstock your tank.

 

[Mattyfelts]

detnitrator isnt a thing honestly, plants and water changes are the way to go, keep up with testing and dont dramatically overstock.

 

[dalto]

Over time given consistent water changes nitrates will always approach (nitrate growth per interval)/(water change percentage per interval). If your nitrates are too high you need to more or larger water changes.

In case you are wondering why this doesn't match the above math it is because PWNAquarist is looking at Nitrates post water change and the above formula is pre-water change.

 

[pbkuhn123]

The author of the linked article seems a bit obtuse. Uh, yeah, you're never going to get rid of every nitrate ion in your tank via water changes. But you can get rid of enough of it via water changes that it can be kept in check at healthy levels. If the author looked closer at his/her own math, he/she would see that the percent nitrate increase per week decreases by 50% after every water change, and will eventually reach a point where the percent increase of nitrate per week will be negligible. Let's see what happens in subsequent weeks...

Week 5: 9.37 units + 10 units = 19.37 units/2 = 9.69 units

Week 6: 9.69 units + 10 units = 19.69 units/2 = 9.84 units.

Week 7: 9.84 units + 10 units = 19.84 units/2 = 9.92 units

Week 8: 9.92 units + 10 units = 19.96 units/2 = 9.96 units

Week 9: 9.96 units + 10 units = 19.96 units/2 = 9.98 units

Week 10: 9.98 units + 10 units = 19.98 units/2 = 9.99 units

If 10 units of nitrate are produced each week and 50% WCs are done each week, the tank will contain no more than 10 units of nitrate. So, yes, the nitrates are indeed "under control" in that scenario.

After being shown the light by an e-mailer, the author then admits that his/her own calculations prove that no more than 10 units of nitrate will be produced in the hypothetical tank, but then mysteriously proclaims that the math doesn't matter and that the nitrates are still out of control by rationalizing a nonsensical scenario of perpetual 100 ppm nitrates. Nitrates CAN be kept in check if you don't let them get that far out of control. And even if you do, nobody's stopping you from doing several large water changes in a row to knock them back to 10 ppm.

Outside of doing 20-50% weekly water changes, I'd recommend Hornwort. Because it grows fast, it consumes a lot of nitrates. Buy a few bunches from your LFS and suction them to the top part of your tank with veggie clips. And, of course, don't overstock your tank.

Thank you for helping clear that up! I appreciate it. Any other plants you would suggest over Hornwort? I tried it once, and it left needles all about.

 

[PNWaquarist]

Thank you for helping clear that up! I appreciate it. Any other plants you would suggest over Hornwort? I tried it once, and it left needles all about.

If you have harder water or a tank temperature of 80 F or higher, Hornwort will be unhappy and shed. It'll stabilize in cooler, softer water. Tethering it to the tank, away from your HOB output, will keep it in one piece.

Duckweed will soak up a ton of nitrates, but is invasive and tough to get rid of. Not recommended.

 

[pbkuhn123]

I do have harder water (KH around 11) and Ph from tap is also about 8.4. Keeps tank stable but well...is what it is...tank tho usually has ph around 7.4 even after water changes. I did have an outbreak of ICH some time back and had tank temp up higher so perhaps that caused the issue too. Thanks for the feedback. To keep nitrates in check I will do a couple more small water changes over next couple days.

 

[trennamw]

What they said. You should be doing water changes that remove as much nitrate per week as your fish put in. If your nitrates are climbing you're not changing enough water.

Plants can offset some of what your fish put in but in most situations they do not reduce water change needs.


Sent from my iPhone with three hands tied behind my back.

 

[Fishfur]

Try some frogbit, or maybe floating water sprite, both are good nitrate suckers. It is also possible to buy a device that does in fact denitrify. Aquaripure, I think, if memory serves me, is a brand name.. not positive I have that right.

But plants also use a lot of nitrates, some planted tanks have almost no nitrates because they get used up. No help if the tank has no plants, I grant you. The device is not cheap, but it does work, if nitrates are really out of control.

 

[Mebbid]

detnitrator isnt a thing honestly, plants and water changes are the way to go, keep up with testing and dont dramatically overstock.

A denitrator is a fairly poor choice of words, but its done with a type of low flow canister filter creating an oxygen free area. In this oxygen free area bacteria will resort to consuming the nitrate, utilizing the attached oxygen, and releasing nitrogen gas thus removing nitrate from the tank.

Its the same type of thing salt water tanks rely on with live rock.

That being said, as long as your tap water doesn't have high levels of nitrates, then water changes are the way to go for nitrate control as others have said.

 

[Fishfur]

That's true.. salt water tanks often use deep sand beds to provide an oxygen deprived area underneath where anaerobic bacteria can thrive. These bacteria consume nitrates, with only nitrogen gas as byproduct. The devices that utilize this anaerobic bacterial process are sort of like a canister, external to the tank.