Where's My Nitrate?

[JezTaylor]

Last week I upgraded tank from a 64l to a 130l (very exciting). I had the tank set up for a week beforehand, then last weekend I moved the fish, old filter and ornaments into the new tank.
 
A bit of a mini cycle seemed to take place in the following days. On Sunday ammonia was up at 0.25. On Monday it looked like it was back at 0 but nitrite had risen to 0.25. On Tuesday nitrite had risen to 0.50 so I did a 25% water change which brought it back down to 0.25.
 
Now ammonia and nitrite are back to 0, but nitrate is yet to read anything other than 0. Is that even possible? Surely for the nitrite to have been removed there must now be nitrate?
 
FYI - I'm using API freshwater master test kit.

 

[Ch4rlie]

Do you have  plants or did you add more plants?

 

[JezTaylor]

Do you have  plants or did you add more plants?

 
I added 8 new bunched plants.

 

[Ch4rlie]

Bunched plants tend to be like egeria densa / elodea or cabomba or vallis, that sort of thing, these do consume a lot of nutrients from the water column, so that may help towards your answer as to why theres very little nitrates.

 

[JezTaylor]

Bunched plants tend to be like egeria densa / elodea or cabomba or vallis, that sort of thing, these do consume a lot of nutrients from the water column, so that may help towards your answer as to why theres very little nitrates.

 
Thanks, that's good to know. Would you say it's a good thing, bad or indifferent? I was going to do a water change tonight, but is it worth leaving it a little longer?

 

[Ch4rlie]

Always a good thing to have plants and lower nitrates is good, i usually advise, depending on what species of fish there are in tank, that nitrates of up and around 40ppm even up to 60ppm can be acceptable, but lower is always better.
 
This is one reason why we fishkeepers do weekly water changes of at least 25 - 50% which reduces the nitrate levels as well as giving the fish nice clean fresh water, dechlorinated of course.

 

[TwoTankAmin]

The API nitrate kit is flakey even when working well. It is the least accurate between O and 20 ppm.
 
1 ppm of ammonia can became a max, of 2.56 ppm of nitrite and 3.46 ppm of nitrate. So .5 ppm of nitrate might become 1.35 ppm of nitrate- if you change no water and have no plants. This scale applies when measuring total ions and not just the nitorgen ions. On the nitrogen scale 1 ppm of ammonia makes a maximum 1 ppm of nitrite and 1 ppm of nitrate.

 

[Byron]

With live plants, and especially fast-growing species as was mentioned, you may never see nitrates (using the API and similar test kits, as TTA pointed out) or eventually they may be low, around 5 or 10 ppm at most.  This is because plants grab ammonia/ammonmium faster and they can take up a lot of it, so they out-compete the nitrifying bacteria.  The plus side is that nitrite and then nitrate is not produced.
 
Comments about nitrate levels raise some alarm bells.  First, it is now being generally accepted that nitrate does poison fish, just as ammonia and nitrite, only more slowly.  The exposure time and the level factor into this.  But the fish we maintain in tropical aquaria are being affected by nitrate.  And when you realize that in their natural habitats nitrate is zero or at most in the very low decimal points, it should be obvious that the lower the nitrate the better, long-term.  For some time now Dr. Neale Monks (and others) has been recommending that nitrate be kept below 20 ppm for all fish, and he has cited some fish that are definitely affected at levels above this, including cichlids.  A nitrate of 10 ppm is safer.  Over on the cichlid site, they also agree that nitrate should be no higher than 20 ppm for cichlids, and even suggest that Malawi Bloat, commonly assumed to be caused by diet, may actually be closer linked to nitrate.
 
Byron.