Cycled tank no longer cycled???

[BBless103]

My 20 gallon tank that I cycled for 2 months has lost its cycle and I don't understand how.

I took two months of a fishless cycle and got my levels to 0 ammonia 0 nitrite and 55 nitrates and I was ready for fish.

Did a 50% water change and got two mollies a Cory and a red shrimp.

Levels were good for two weeks 0 ammonia 0 nitrite 30 nitrates.

Did a partial water change and got nitrates to 10

Next day shrimp dead 8.0 ammonia 2.5 nitrite 70 nitrates.

Quickly did 70% water change with prime and removed my fallen friend.

Levels won't stay down and I need advice

 

[HarpyFishLover]

What probably caused this is the sudden addage of fish.

Never add more than 2 fish at a time, as this can cause a crashed cycle.

My amateur advice is to do a 90% water change once a day. If possible, remove a few of your fish to another CYCLED tank.

Your tank was probably only marginally cycled, and so adding effectively 4 fish was not good for it.
Also, this sort of thing should be posted in "Tropical Fish Emergencies" and probably would have been responded to faster if it had been there...
Maybe a moderator could move it there?

 

[Gruntle]

Doing a fishless cycle means you can add a full stock to the tank immediately, so I'm not sure this is the cause of the issue.

With a sudden jump to 8.0 ammonia, there is something that has caused the jump. Are you talking about a red cherry shrimp, one of the really small ones? It shouldn't cause an 8ppm spike in ammonia by itself. Did you add anything else to the tank? Have you overfed the fish (fish should be fed once a day, no more food than the size of one of their eyes)?

I'm perplexed for you... Please supply updates. Thanks.

 

[BBless103]

Yes it was a very small cherry shrimp. Less than an inch.

Water today when I got off work was 4.0 ammonia 2.0 nitrate and 20 nitrate. Ph 8.0 mollies doing fine cory is acting sluggish did a 80% water change with prime.

Still perplexed as I am new to the whole nitrogen cycle and didn't expect such a spike after two weeks

 

[BBless103]

Also I only feed one a day usually 1 flake per inch of fish so currently 5 flakes crushed well for the 3 mollies and cory as well as one cory disc(algae)

 

[Mrscmurray]

Have you tested your tap water at all? My logic is that this happened after a water change.
If the tap water tests OK then I would advise multiple daily changes of 50% to try and get the levels down again. There isn't any chance something got in the tank while cleaning? An aerosol or something?

8 ammonia is crazy high, I've never heard of anyone with it like that before.

Sent from my HTC Desire 626 using Tapatalk

 

[BBless103]

I don't use any aerosol cleaners. I only use washcloths and water anywhere around tank stand and a swiffer sweeper wetmop on floors.

Untreated tap water after 24 hours with stirring tests 0.25 ammonia 0 nitrite and 25 nitrates
Primed tap water tested same way was 0 ammonia 0 nitrite 5 nitrate

 

[Gruntle]

The only time I've seen ammonia at 8ppm was when a friend of mine made the mistake of introducing a freshwater crayfish to his tropical tank. The cray grabbed and killed a large fish, and stuffed it under a rock for later. The water was so cloudy we had to empty the tank to find out what had happened.

 

[BBless103]

Added additional ceramic media to filter hoping to increase bacteria