Cycled the tank, did a water change = nitrite spike

[NBCGLX]

I've been going through a fish-less cycle since just after Christmas, and other than a snag I had with pH (discovered I have soft water; i.e., barely any buffers in the water) that was rectified, the cycle has been going as expected. For the last four days ammonia and nitrites were dropping to zero overnight after dosing the tank to 4ppm of ammonia. THIS guide recommends a 90% water change after consistent 0 ammonia/nitrite tests to rid the tank of nitrates, so I did that last night. I then (maintenance) dosed the tank with ammonia following the same guide (I think 1ppm if I recall correctly) knowing that it would be at least 24 hours before any fish were added. Came home from work tonight and tested the water. pH is fine. Ammonia is 0ppm. Nitrites are off the chart!

Any clue why this happened??? No other changes were made to the tank.

 

[ScotJudd]

My only thought is that you added nitrites from the tap. Have you checked your tap water?
1ppm ammonia should not have produced that high a nitrite reading even if you had no nitrite to nitrate bacteria present.
Just a stab in the dark though!


Sent from my iPhone using Aquarium Advice

 

[Yorg]

Hi NBCGLX:

Hard to imagine what might have happened to produce that big a nitrite spike, especially since all you did was a water change.

I'd keep testing for a day or two and see if the nitrite comes back down to zero. If it does you should be fine. If it doesn't, keep adding ammonia until you get to 2ppm (that's plenty for your ammonia-eating bacteria to feed on) and see what the nitrite does then.

It sounds to me like you're doing everything right, but every cycle I've ever done, fishless or otherwise, has been different.

-Yorg

I've been going through a fish-less cycle since just after Christmas, and other than a snag I had with pH (discovered I have soft water; i.e., barely any buffers in the water) that was rectified, the cycle has been going as expected. For the last four days ammonia and nitrites were dropping to zero overnight after dosing the tank to 4ppm of ammonia. THIS guide recommends a 90% water change after consistent 0 ammonia/nitrite tests to rid the tank of nitrates, so I did that last night. I then (maintenance) dosed the tank with ammonia following the same guide (I think 1ppm if I recall correctly) knowing that it would be at least 24 hours before any fish were added. Came home from work tonight and tested the water. pH is fine. Ammonia is 0ppm. Nitrites are off the chart!

Any clue why this happened??? No other changes were made to the tank.

 

[NBCGLX]

My only thought is that you added nitrites from the tap. Have you checked your tap water?
1ppm ammonia should not have produced that high a nitrite reading even if you had no nitrite to nitrate bacteria present.
Just a stab in the dark though!


Sent from my iPhone using Aquarium Advice

Yes, tap water is 0 for everything and pH is right around 7.2 (after sitting for 24 hours). And I agree, 1ppm ammonia in no way should've spiked nitrites that high.

Hi NBCGLX:

Hard to imagine what might have happened to produce that big a nitrite spike, especially since all you did was a water change.

I'd keep testing for a day or two and see if the nitrite comes back down to zero. If it does you should be fine. If it doesn't, keep adding ammonia until you get to 2ppm (that's plenty for your ammonia-eating bacteria to feed on) and see what the nitrite does then.

It sounds to me like you're doing everything right, but every cycle I've ever done, fishless or otherwise, has been different.

-Yorg

Yes, I've done this a few times in the past (fresh and salt) and none of the cycles were alike. I've just never experienced this type of bizarre reaction. I'm going to continue monitoring the water and see what happens.