# Nitrite spike in cycled tank



## stewardwildcat (Feb 24, 2010)

Hi all,

I know nitrites and the nitrogen cycle are covered in depth on this forum and I know how it all works. My tank is 3 months old and has been cycled for 2 of those months. I did a 50% water change yesterday and I was pretty careful to let the dechlor (sodium thiosulfate) to let mix in before pouring water from buckets into the tank. The water here does not contain chloramines only chlorine. I left for the day and came back and there were several dead fish and a number of dead RCS. All of the inhabitants including the snails were trying desperately to be at the top mm of water. I immediately tested nitrites and ammonia. Ammonia was a slight shade darker than 0ppm but there were dead animals in the tank so thats not too suprising. The nitrites were over .5ppm, I did another 50% water change and retested nitrites to make sure they went down and they did by 50%. I woke up and retested nitrites again this morning and they were slightly less than .5 ppm. I again did another water change to lower them and left the water level a little lower to make sure there was a good oxygen mixture from the surface to the animals had a little easier time breathing. 

This has happened once before (very early on in the cycling) when I did a large water change, but that time i know it had a mini cycle but the ammonia and nitrites were gone within 24 hrs. I have an established biofilter and it keeps the tank at 0 NH3 and 0 NO2 all the time (except after large water changes it seems). What could be going on here? Why if I did damage the bacteria colonies (which I didnt clean the filter this weekend) did only the Nitrite eating bacteria suffer? I will do water changes for the next 2 days but I am away for work for a week and am not sure what to do. 

Please help!


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## Mr. Fisher (Mar 24, 2009)

a nitrite spike in a cycled aquarium usually suggests something died. Check your filter thoroughly. check your tank and remove all dead fish and shrimp. I bet there are still dead fish/shrimp in the tank/filter.

You can use Prime which detoxifies ammonia, nitrite and nitrate.

Keep doing >50% water changes daily till the Nitrite and ammonia are at 0 ppm. Keep doing water changes today till you notice an improvement.

You can also buy purigen to absorb all the nitrite/ammonia.

Prime and Purigen are planted tank safe and do a great job during emergencies.


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## stewardwildcat (Feb 24, 2010)

Well I know the spike killed a number of things. I sucked out all of the shrimp and fish i could see. There are a few underneath some driftwood that i could remove with some pain but there are only a handful. I did not open the filter other than to throw in some carbon this morning to help remove anything else that might be in the system. I know nothing of purigen (other than what it does) and I don't know if it will ruin my cycling? I can go take the filter apart and dump the dead things in it, I am sure there are a few guppy fry and a few dead shrimp. Ack I feel so awful not being able to keep a stable environment for my babies.  I dont even know what I am doing wrong. All that is in the tank are RCS, and guppies and two baby leuscistic plecos.


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## Mr. Fisher (Mar 24, 2009)

In order to keep the current inhabitants alive you will need to remove all dead fish from the tank and the filtration system.

You will also need to do >50% water changes till the Nitrite and ammonia read O.

Everything else is secondary.

.5 nitrite and .25 ammonia are enough to kill everything except snails.

Purigen and Prime do not affect your cycle, nor do they neg affect your plants. the combo of the two will save you rtank, which is crashing.

Who cares at this point what the cause of the spike was. Chances are it was a dead fish.

How is your local water chemistry?


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## stewardwildcat (Feb 24, 2010)

Water chemistry for NH3 and NO2 are 0ppm at the tap. We only use chlorine here in tucson and I dechlor and mix the water before dumping in the tank. Ph is 7.5-8 and varies depending on the water source and how much is being used around the city.


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## Mr. Fisher (Mar 24, 2009)

yeah, something is dead and rotting in your tank.


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## stewardwildcat (Feb 24, 2010)

I cleaned it all out. Except for a few bodies in the prefilter sponge that I cannot get out, I cannot see any dead anything in the tank.


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## Mr. Fisher (Mar 24, 2009)

stewardwildcat said:


> I cleaned it all out. Except for a few bodies in the prefilter sponge that I cannot get out, I cannot see any dead anything in the tank.


it's important to rid the tanki of all the bodies.


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