Acceptable Nitrate Levels for Cardinal Tetras

dereks

AC Members
Mar 7, 2006
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Checking my water at it's worst, just before my weekly water changes, my nitrates have risen up to 5ppm. I'm assuming this is acceptable sincve I've heard it's rare to have 0 nitrates. However, I've heard that my cardinal tetras can be sensitive to nitrates, so I'd like to keep an eye on them. What levels should make me comfortable, uncomfortable, and when do I need an early water change?

Thanks!
 
Checking my water at it's worst, just before my weekly water changes, my nitrates have risen up to 5ppm. I'm assuming this is acceptable sincve I've heard it's rare to have 0 nitrates. However, I've heard that my cardinal tetras can be sensitive to nitrates, so I'd like to keep an eye on them. What levels should make me comfortable, uncomfortable, and when do I need an early water change?

Thanks!

How old is the test kit?
 
The test kit is brand new. Is 5ppm really low or something? The tank is lightly stocked, about 25 inches of fish in a 37 gallon. I know java fern isn't known for soaking up nitrates but there is a lot of it in there, I'm guessing that helps some too. Weekly 25% water changes probably helps too, is this too often?
 
Nitrate toxicity is very relative depending on the species and age of the fish among other factors...you can see aquaculture studies with very high concentrations (in the 100's to 1000+ ppm) needed to induce a short-term response in some hardier species, while fairly low concentrations (within levels we normally see in aquariums) may effect larval stages or fertility and/or show physiological effects to adult fish over the long-term. That being said, you'll see people say they are fine at these same levels as well. Heck, a lot of people (including myself) dose KNO3 for plant purposes and never see a negative reaction from the fish...at least nothing notable.

It's really hard to say one way or the other. I'd say that 5 ppm is really nothing to lose sleep over for just about any fish you could keep. I see nothing wrong with what you are doing. Just make sure you're following the test kit instructions to the letter...the API NO3 kit is easy to mess up with the different bottles and shaking required, and it's possible to get false readings.
 
Cardinals originate from tributaries of the S.A. Amazon river - basically from the same types of waters that discus habituate, being soft, very low in TDS's, and low in nitrates. So from a genetic standpoint one may conclude they would not do well in a high nitrate environment, much the same as discus, which can experience some discomfort at nitrate levels as low as 20 or more ppms. While I'm not suggesting that that particular level will cause a problem for Cardinals, I would expect that levels in the 40 ppm or over may be a cause for concern. Large weekly wcs should ensure nitrates do not begin to reach those levels in a planted tank.
 
Cardinals are popular in many planted tanks where nitrates are consistently maintained at 30-40 ppm. They do just fine. 5 ppm is no cause for concern.
 
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