Nitrite Sudden Rise And Plummet

[NewBea]

As far as I know my tank was fully cycled (fish in cycle) I watched the ammonia going up then couple of days later the nitrite followed which cleared fairly quickly after about 3 days. I allowed an extra week while monitoring the levels and all remained at 0.
Then I decided to go for my next batch of fish (4 guppies) and before I went to the shop I've done a water change and rearranged the plants a bit as well as I wanted to get some fresh ones. In stirring up the gravel loads of bits started floating around in the water but I thought it would settle and that would be fine.
I got the new fish and all was good until the next day when I tested the water again. Nitrite all of the sudden was up to 2.0 even though the ammonia was 0! Quick 50-60% water change and the level was down to 0.5. Which I know is not ideal so I've done another 25% water change later that day.
By the next day the Nitrite level was down to 0 again - a bit baffled.

Can someone tell me if the gravel stirring could have cased the sudden rise of Nitrites? And what caused the sudden drop to 0 the next day - the good bacteria in the filter?

I've read in some of the topics that most of the harmful stuff sinks to the bottom of the tank. I do regular vaccum (at least once a week).

I was expecting that adding the new fish would first increase ammonia - then nitrite levels later as the tank goes into a secondary cycle with the additional fish. In line with this the ammonia levels today were 0.5 (so another large water change was carried out to push the levels under 0.25) and now just waiting to see what happens with the nitrites again.

Also can someone tell me if this "second cycle" would be any quicker than the first one?

Some details in case you need it: tank 100l, so far I had 2 sailfin mollies, 4 mollies and 2 swordtails + the 4 new guppies

Thanks for the advice in advance.

 

[NewBea]

Does anybody know why the Nitrites have peaked so badly?
I'm just trying to make sure that I can avoid it in the future if I can help it.

 

[KCB]

It looks like you might have had a mini cycle when you added some more fish, you may have just missed the ammonia spike.

 

[NewBea]

It looks like you might have had a mini cycle when you added some more fish, you may have just missed the ammonia spike.

Within a day from adding the fish? But the next day the ammonia started going up

 

[KCB]

I'm not 100% sure but here's what I think happened: As the bacteria were receiving more 'food' than usual, this may have caused them to multiply and now they are at a level where they can cope with your bio-load, hence why there is now no ammonia or nitrite anymore. I'm not sure if it can happen that quickly but it's the only thing I can think of . If it's gone now I wouldn't worry about it until you next add fish.

 

[The Taffy Apple]

Less than a week for a full fishless cycle seems awfully quick.... did you add a source of mature media from someone or from another of your tanks?
If not, i would dare to say you may not be cycled, and would continue to carry out as much water changing to get the Ammonia and NitrItes down to '0'.
What test kit are you using?

Terry.

 

[NewBea]

Less than a week for a full fishless cycle seems awfully quick.... did you add a source of mature media from someone or from another of your tanks?
If not, i would dare to say you may not be cycled, and would continue to carry out as much water changing to get the Ammonia and NitrItes down to '0'.
What test kit are you using?

Terry.

Hi Terry,

No, it's just been a week since all the levels were 0. It wasn't fishless cycle either.
I had the tank for 2 months with no fish - where I assumed the cycle was done - only to find out from this forum a bit too late that it would have needed ammonia as well. (the book I had on the subject didn't mention this just pretty much said let the tank mature for a few weeks before adding the fish) I added 8 fish (based on advice from fish shop - which I now know was too many) so it meant I had to do a fish in cycle. Loads of water changes and API master kit testing every single day. The fish in cycle took 4 weeks before the readings were 0 and I waited another week just to make sure it's stable.
I only actually joined this site about a week after I had my initial batch of fish and have been receiving heaps of good advice ever since.

I hope this explains.

I'm not 100% sure but here's what I think happened: As the bacteria were receiving more 'food' than usual, this may have caused them to multiply and now they are at a level where they can cope with your bio-load, hence why there is now no ammonia or nitrite anymore. I'm not sure if it can happen that quickly but it's the only thing I can think of

. If it's gone now I wouldn't worry about it until you next add fish.

Maybe.... it's just a bit weird.
I changed 25% water again today as ammonia was between 0.25 and 0.5 this morning. Nitrite was still at 0. Will test again tomorrow.