I have a new tank that is cycling (despite using 100% water, excess plants and a "seeded" sponge filter from an established tank). I'm now in the nitrites through the roof phase. I am dosing Seachem phosphate, potassium, excel and trace as well as CO2 from pressurized system. I am NOT yet dosing NO3 (nitrate). Am I correct that the plants can draw off the nitrites and that there is no need to dose NO3 (nitrate) until the tank finishes cycling?
I think that would be correct....but I don't think "high" nitrites on a test kit scale would actually be high nitrogen as far as plants are concerned. Nitrite test kits are calibrated to detect very small amounts of nitrite since it's so much more toxic to fish than are nitrates. So you get readings of somewhere in the .5 - 2.0 ppm range on a test kit and it's considered high, wheras for nitrate we are probably looking to have somewhere closer to 10 - 20ppm and that's considered not very high. Posting your exact ppm reading would be more helpful.
Personally I would probably do water changes to lower nitrite somewhat and then add nitrates back in for the plants, especially if you have fish in the tank. If you don't, you might want to add a little bit of nitrate anyway, it probably won't hurt, especially if you have lots of plants and co2 injection which could cause the nitrogen to vanish suddenly overnight when things get established, and then you end up deficient.
Thanks Carissa. It seems odd to me but NO3 (nitrAte) is also consistently testing fairly high (40 ppm) in this tank over the past week, even though (1) there is pretty good plant growth, (2) I am not dosing NO3 and (3) the tank is obviously cycling. I thought NO3 would not get that high until after NO2 (nitrIte) dropped.
When a tank cycles you will see first a mixture of ammonia and nitrite, then a mixture of nitrite and nitrate as the biological filtration builds up. You are probably adding more nitrogen on a regular basis than your plants can take in right now, so you'll end up with excess nitrate since that's the end product of the nitrogen cycle. If you want a tank with lower nitrates without doing water changes, you'll have to have a fish bioload that produces less nitrogen than you are adding now, or more plants or faster growing plants to take it in faster.
Last edited by Carissa; 11-21-2007 at 02:01 PM.
No, they cannot use them [NO2-].
Originally Posted by mpe1329
You have the proof right in front of you :thumbsup:
If plants did, then why are they not removing it when everything else is in non limiting supply?
We see this pattern with any new tank that lacks bacteria when folks add NH4 for fishless cycling.
The NO2 builds and persist for abouit the same time as a non planted tank.........
now if you want to accept that plants use NO2...........as Dianba Walstad claimed they do in her book, a simple experimental test that most any aquarists can do, and have............falsifies her hypothesis here.
The rates of NO2 decline are similar for both the planted and non planted tanks with respect to NO2 in the start up phase.
This suggest that plants are not using NO2(a very wide range of species appear not to put a dent in the NO2 decline).
If she or someone else can show that the NO2 are reduced, I'd like to here about it in a submersed planted tank, not a duckweed culture in petri dishes.
It's nice to suggest something, however, the observations in planted tanks and the test kits really are not lying..............
So what to do about them?
Large water changes, add zeolite from day one etc.
As far as levels of NH4, NO2, NO3...........NH4 is likely from some rot etc or die back, leaching from plants............this is fairly quickly converted to NO2.........this bacteria forms fast, or plants gob up the NH4...................then you are left with some NO2 that will persist.
NO3 can be leached from the plant's reserves when they came in, the cell's vacuoles store a large amount of NO3.
And perhaps there's a little NO2-> NO3 bacteria present on the plant's themselves. Test kit error is high with NO3 test ktis also, it is suggested to use a set of calibration standards, made from DI water and KNO3 to check the accuracy of the test kit.