Mollies, nitrite and nitrates. Please help.

[Mrs.Henry]

I have a 40 gallon tank with 6 Mollies. This tank has had fish in it about 4 weeks and had a 3 weeks fishless cycle before adding anyone. I over the weekend had a very slight amnio raise. That is now gone. Now nitrite and nitrates. What should I do?

 

[Byron]

T%his is a new tank, so the first problem is, how did you cycle it? It is appearing that it was not fully cycled, so we need to know just how it was done.

If you are seeing nitrite--note, this is nitrite with the "i", not nitrate with "a"--this is deadly to fish, especially mollies. A major partial water change (60-70% of the tank volume) should be done immediately. Use a conditioner. If you can get Prime or Ultimate, both of these conditioners also detoxify nitrite and will help here. Do the partial water change every day until nitrite is zero (and assuming ammonia also is zero).

Fish are internally affected by ammonia and nitrite so there is no way of telling what may have been done, and if the fish will live through it or for how long. What's done is done. Good luck going forward. And welcome to TFF.

 

[Mrs.Henry]

Thank you for the reply. The first 3 weeks that this tank was up there was no fish in the tank .. Only rocks and filter from a previous well cycled tank at about 3 and a half weeks I started adding Mollies.. Fish have been in this tank for about 4 weeks. I thought the old rocks and filter would cycle the tank. ???

 

[Byron]

Thank you for the reply. The first 3 weeks that this tank was up there was no fish in the tank .. Only rocks and filter from a previous well cycled tank at about 3 and a half weeks I started adding Mollies.. Fish have been in this tank for about 4 weeks. I thought the old rocks and filter would cycle the tank. ???

Filter media from an existing cycled tank generally can be used to get the cycle going on a new tank, but there could have been other factors here. If I understand correctly, the tank ran minus fish for three weeks with the filter from another tank, then six mollies were added and for four weeks no ammonia or nitrite, then this weekend ammonia appeared and now nitrite and nitrate.

The advice in my previous post stands. In addition, you could get a small bottle of bacteria, like Tetra's SafeStart, or Seachem's Stability. I have used the latter in an emergency with good results.