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Can waer changes make nitrates go up?

2K views 16 replies 9 participants last post by  dbw27 
#1 ·
I went thru a mini cycle due to a course of meds. Cycle seems to be back to normal but I can't get my nitrates down. Each day I'm testing and it's at about 40, I do a 50% w/c and the next day it's back at 40. Hell, Sunday I changed out about 75% of the water through out the day with multiple w/c. I'm not overfeeding - I' barely feeding at all. Not overstocked.

I'm wondering if my nitirates could be increasing because of the ammonia in the chloramines? I use Prime. Perhaps I'm adding back as much ammonia as I'm removing when I do w/c and it's converting into nitrates overnight? Is that possible?
 
#8 ·
My api nitrate test kit shows tap water coming out at 10/20 ppm (same color on chart for both). My 20g long has no fauna (except snails) and until this Sunday a lot of plants so i actually got nitrates down to 0ppm (first time I've ever seen this in a tank) so doing a water change actually added nitrates back in.
 
#9 ·
I use RO water for my heavily planted aquarium. I practice very good tank maintenace. My 'high nitrate' levels really weren't high at all. The problem was with my API Nitrate test kit. I bought a Seachem Nitrate test kit and nitrates tested much lower.

I confirmed the results from the Seachem kit using their reference solution. As a second test for accuracy, I mixed up additional reference solutions using instructions posted by Hoppy ,under a sticky on this website, under the 'Fertilizers and Water Parameters' section. Once again, it proved my API Nitrate test kit to be inaccurate and matched the Seachem test results.
 
#10 ·
Chloramines are rarely more than about 2 ppm, so, no, massive water changes with water that has chloramines will not result in rising nitrates like you are describing.

If the tap water has 5 pppm, and the chloramines contribute 1-2 ppm, then a 100% water change should show no more than 10 ppm or a bit lighter color.

Here is what I have seen a few times:
There is some source of nitrates in the substrate.
When I do a carefully measured water change (whatever that means) of 50% I would expect the NO3 to be cut in half. But it is not, quite.
When I do the same volume of water change, but take the water from the substrate (such as a gravel vac, or a more complex method with a planted tank) then I do see the NO3 cut in half.

I still do not think this is the only cause of such quickly rising NO3, but you might start by trying this:
Dig a corner out down to the bottom of the tank and take the water change water from there, hopefully pulling it through the substrate rather than from the water column. If you can dig more holes and take water from several locations this would help.

Have you added any fertilizer tablets that might be escaping from the substrate?
 
#15 ·
Thanks for the replies.

I also have the Seachem Multi Test kits and as well as the API, and I'm getting the same readings on both (used API to test the tap tho). So I don't think my tests are off.

I've been hesitant to vac the gravel because I'm recovering from a mini cycle after medicating the tank. I've added some Dr. Tims One & Only and I don't wanna suck it back up. But now I'm also wondering if the product might be causing the problem? I figured I'd do a small gravel vac this weekend, hoping the product has had time to work it's way into and adhere to the filter media.
 
#16 ·
Nitrifying bacteria MIGHT "cause" nitrate problems in 2 ways.

1) Ammonia or nitrite is entering the tank and the nitrifying bacteria are turning these into nitrate. This is not really a problem: you did not want the ammonia and nitrite staying in the form it is in, do you? I didn't think so. At least NO3 is less toxic.
So the bacteria are not "causing" the high nitrate problem, they are showing you there is an ammonia or nitrite problem.

2) The nitrifying bacteria might be dying off, and dead organisms contribute ammonia to the water. Then the remaining bacteria turn the ammonia into nitrite, then nitrate. If this is what is going on, you need to find out why things (microorganisms) are dying in the tank.

The bacteria in Dr. Tim's ought to cling to the filter media and any other area with good water movement. Nitrifying bacteria do not really care for being deeper in the substrate where there is lower oxygen levels. But you are smart to hold off doing water changes for several days when you have just added this product.

______________________________________________________

Recap:
High nitrates that come back pretty fast after a water change means there is some source of nitrogen in the tank.
The beneficial bacteria might be turning ammonia or nitrite into nitrate, which simply moves the problem back a step: There is ammonia or nitrite entering the tank.
Things that die (animals, microorganisms, plants) have nitrogen in them in various forms. When things die the nitrogen is digested by many things and a lot of it ends up as ammonia.
Fish food is in the same category as 'dead things'. The protein in fish food has nitrogen that can become ammonia whether it is eaten by fish or falls to the floor and is eaten by microorganisms.
 
#17 ·
Ammonia is sky high in my tap water. Doing water changes wreaks havoc on my water parameters. Even my lfs told me to limit water changes.

Therefore, I may try to switch to RO (difficult on a grad student budget). However, yes, water changes can cause trouble. I have perfect water parameters (zero ammonia, zero nitrites), but if do a water change, often havoc.

dbw
 
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