# Nitrate levels after water change



## starfire57

I tested my water tonight and found the ammonia and nitrate levels were a little high, so I did a 25% wc on my 46 gallon. After about 5 mins I retested the ammonia and nitrates, the ammonia was back at normal but the nitrate level was way high. I have retested three times and it comes out the same. I am doing the test correctly and I have also tested my source water and it was at 0, So why would the nitrate go up it has never done that before.


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## Mikaila31

what is "way high"? 

are you fish-in cycling or fishless cycling?


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## starfire57

The tank has been up and running for at least six months now. I have done wc before with this tank and nothing like this has happened before. Not even with my old tank which I took down to start the 46, and it was started with water, gravel and fliter media from the old tank. I have since then changed the fliter media a couple of times. Previous water test have been within the normal ranges.


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## pinetree

Sounds like something has disrupted your tank's cycle. 

When I was doing a fishless cycle, I started to get bizarre nitrite readings. They would go up to about 2ppm, but then appeared to start dropping after that instead of continuing to increase. After I'd do large water changes (about 80%), then they'd increase again to a solid 2ppm. It became obvious that the nitrites were just going so high I was getting false low readings with the API test kit. 

Maybe something similar is happening with your nitrate readings? Which test kit do you use?


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## Mikaila31

starfire57 said:


> The tank has been up and running for at least six months now. I have done wc before with this tank and nothing like this has happened before. Not even with my old tank which I took down to start the 46, and it was started with water, gravel and fliter media from the old tank. I have since then changed the fliter media a couple of times. Previous water test have been within the normal ranges.


what are the levels? what is you maintenance routine, like wc frequency? 

Changing the filter material removes your good bacteria and can disrupt the cycle. This is not recommended. Filter media does need to be replaced unless it is falling apart. When you do replace filter media only do 1/3 at a time max, then wait 2 weeks. Otherwise you will go through a mini cycle, which is what I think you are seeing, but its hard to say without more info.... When the filter media gets dirty you rinse it out in dechlorinated water and put it back in the filter.


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## ron v

What am I missing??? Ammonia is "normal" which I assume is 0. No mention of nitrite so that must be 0 also. Nitrates are high... doesn't sound like a problem with the cycle to me.


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## emc7

Agreed. higher nitrate after water change is interesting, not a failed cycle. Did you scrape off a bunch of algae or stir up the gravel and disturb uneaten food. It is possible you just uncovered some gunk that was converted to nitrate by your filter.


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## pinetree

The original post said the ammonia and nitrate were high, that's why I suspect the cycle may have been disrupted. My cycled tanks have always had 0 ammonia readings. They didn't mention nitrite, so I dunno.


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## emc7

Short-term ammonia spike followed by raised nitrate is consistent with a dead fish, overfeeding or other introduction of extra organic matter. The fact the ammonia came back down means, at worst, a mini-cycle now over.


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## starfire57

Did another small wc yesterday Niatrate levels still at 40, I use the liquid test kit made for freshwater aquariuns. My flitration is 2 pequin bio-wheel fliters, one is a 100 and the other one is a 150, I took the fliter media out and emptied the carbon out of them so I would just have the poly pad. I did this so I could keep the poly pad in all the time and just replace the carbon pad. That way if I ever had to treat for ick or something that needed the carbon removed I would still have flitration. So when I removed the carbon of course the pads got rinsed out, could this be why I am having high Nitrate levels. I will continue to do small wc's until the levels go down. I did not even consider that my tank was going through a mini cycle. Thanks for pointing that out, now I don't feel so frustrated.


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## ron v

If your ammonia=0 and nitrite=0 you are not going through a mini cycle. Just remember that a large part of your cycling bacteria are in your filter media. Take care of it. Don't throw it away. A filter pad usually last me two years or more. Use dechlorinated water to rinse. The only way to get rid of nitrates is water change. Don't be afraid to do big water changes. I have been known to do 90% at a time... I don't understand why nitrates are not coming down with a water change. A 50% water change should reduce nitrates by 1/2. That is math... I suspect your test kit.


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## Obsidian

I have had nitrates rise again following a water change. In my case it has to do with filter care, or lack thereof. I need to be more on top of those in my 100ga. But I have a fairly standing problem with higher nitrate in that tank even with good maintenance. When it gets up to 40 I start doing larger water changes. I will do anywhere from 2-3 40% changes over the course of several hours (i.e. do a WC wait an hour and do another one, if it starts at over 40 then I will do a 3rd one an hour after that just to make sure it gets down there. I can usually get it back to around 20 doing that. The fish handle this just fine).


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## Mikaila31

What does your tap water read for nitrates? 

40ppm is not really a issue IMO, but I would keep a eye on ammonia for a while. Some of my tanks run around 40 ppm, my rummy nosed tetras are fine with that and emperor tetras and boesemani rainbows spawn regularly.


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