Did I break the cycle of my new tank?

[erollin]

Hello everybody,

I got my first tank (38 Gal) more than 1 month ago and started a cycle with three swordtails.  The day after the introduction of the fishes, we wake up with 7 small babies!  But this is another story.  After the delivery, the female got sick (fongus I think) and we tried to save her with commercial product for ick/fongus etc...   I was not able to save her, she died one week after. (I realize now that I should have left Nature the care of the mother...)

Anyway, I now follow the concentration of NH3 and NO2- before introducing new fishes, but I do not see what I expect.  The NH3 seems to stabilize/decrease (1ppm) slowly for more than 1 week now... and no sign of NO2- (a short peak 4 days ago at the limit of my test kit, and YES my kit seems OK, I tested it...) .

So, is it possible that the medication that I used killed the bacteria that convert NH3 -> NO2-  (so that I needed to restart a new cycle) but kept the small amount of the other kind of bacteria, so that now, as soon as NO2- is created, it is converted to NO3-?

I don't worry about my aquarium, I know that one day, my tank will be cycled, I just want to know if it can happen and learn more about my new aquarium.

Thanks a lot,
Etienne

[BigDaddy]

Some medications can interfere with the biological filter.  Others will also increase the waste products produced by fish, causing elevated nitrogen levels.  It could be either of the two.

That being said, you talk about your ammonia and nitrite levels, but what are you nitrATE levels at (NO3)?

If you have 0 nitrite 0 nitrate and climbing ammonia, it would sound like the former.

If you have measurable nitrate, little to no nitrite and climbing ammonia, it may just be a result of the latter.