Nitrates disappearing?

  • #1
I've been cycling my tank for nearly two weeks now. The bacteria can easily get ammonia down from 4ppm to 0ppm in 24 hours and I'm just waiting for the nitrite -> nitrate bacteria to catch up. About two days ago my nitrites were off the chart and my nitrates were at roughly 40ppm. Yesterday the nitrites were still off the chart but the nitrates went down to 20ppm. This morning when I checked there were barely any at all! What's happening to them?

It's a 20 gal (high) tank and I'm doing a fishless cycle
I have a few plants (2 Amazon swords, 2 Dwarf hairgrass) and a few MTS'
I use the API master test kit.
  • #2
The plants might be using up some nitrates, but I'm not sure if they could use up that much. Are you sure you're shaking the bottles properly?
  • Thread Starter
  • #3
Yeah, I'm near certain.

Bottle 2 for 30 seconds and the test tube for a minute.
  • #4
you shake the bottle really hard?

nitrate doesn't go anywhere unless it is consumed or you remove it with a water change.

I never test nitrates in cycle...there's no point.

btw,adding that ammonia just makes your cycle longer.
when nitrites drop down,then you can add ammonia to keep cycle going/test,but 4 ppm is too much.
do 1 or 2 ppm.
Jocelyn Adelman
  • #5
I found it best to really bang the bottle around instead of shake it.... I bang it against my counter... I believe there is crystals or something that settle and stick to the bottle, so I make sure to bang all sides...
  • #6
Your high nitrites may have killed off your BB which is why your nitrates have dropped off. It would have been best to do a couple of large water changes to bring down that nitrite so it doesn't stall your cycle.

What are your water parameters now including pH and temp? Are you using a bacteria supplement?
  • Thread Starter
  • #7
I checked my nitrates this morning and they're going back up again.

My current water parameters are:

78 degrees celsius
Ph is at a steady 8.0
Ammo at 0
Nitrites still off the chart despite 30% water change
Nitrates are at 20 ppm as of the last time I checked.
  • #8
30% won't be enough to bring it down and would mean your nitrites are much higher than 5. I'd get nitrites down below 1 by doing larger water changes. Then dose ammonia to 1 this time to give your nitrite eating bacteria a chance to establish itself.

Are you using a bacteria supplement?
  • #9
Hi, I see this happen a lot in fishless cycling. Fishless cycling is very unique, especially when using pure ammonia because there are no organics that normally accompany ammonia when it is broken down in food, waste, plant matter etc. You have many types of bacteria in your tank, there are the nitrifyers which you are testing for but there are also heterotrophic bacteria that grow and compete for space in any aquarium. They break down the organics.

When you first fill up your tank with water, both types are there in small numbers. The heterotrophs go to work on consuming the organics in your water column itself, eventually when they run out of food, they have the ability to switch roles and consume nitrates albeit very inefficiently in comparison to the nitrifyers. Normally people associate de-nitrification only happening in an oxygen free environment but in this type of unique situation they can switch roles and become de-nitrifyers in an aerobic environment.

You don't want to ever let your nitrites get above 5.0, it will stall your cycle. Even though the bacteria need ammonia and nitrites to multiply when it is too high, it has the opposite effect of inhibiting the growth of the bacteria.

I would do a 90-100% water change, dose ammonia to 1.0-2.0, no higher, while in this high nitrite phase, wait for ammonia to drop, test nitrites, if nitrites are still high, give it another 24-48 hours to catch up before re-dosing. The ammonia converters, nitrosonomas won't die, they do not have to be fed daily. This will allow your cycle to finish up

Edit: Also, I would put a small pinch of fish food in a nylon sock and put it into your tank. The nitrite to nitrate bacteria need phosphates to convert over and some people do not have enough in their source water alone.

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