How long can a tank stay cycled without fish?

[mustangmp96]

Question speaks for itself so I’ll explain my situation. My 36 gallon bow front has been dry for sometime now. When I drained it I left some gravel, dirt, and some rocks in it. I removed a decorative log and a large piece of rock and put them in a bucket. I cleaned all the hardware (filter cases, heater) and replaced the air stones and tubing.

I did all of this at least 6 months ago, but maybe 8. Tonight I reset the aquarium and filled it.

Afterward I tested the levels just to see where they might be at. I expected all my levels to be at 0, but my ammonia was around .25 ppm, nitrite was 0, and nitrate was between 80 and 160.

Long story short, TLDR, whatever, this tank has been dry for at least 6 months. Could it still be cycled?

 

[BBradbury]

Hello mus...

A cycled tank won't have a trace of ammonia. There's likely some residual waste material in the gravel. When you added water to the gravel, the waste began to dissolve. The dissolving waste combined with oxygen from the surrounding air has started to grow the bacteria colony. You've started the nitrogen cycle.

B

 

[mustangmp96]

Thanks B