Established Tank Vacant For A Month Now High Ammonia???

[Convict small fry]

Hi,
I have a 10 gallon tank I want to use for a guppy breeder about a month ago this tank was running great bio with a betta and small school of tetras. I moved betta and tetras to a 30 gallon tank and left the 10 gallon vacant for a month. I tested the water two weeks ago as a precaution before adding guppies and the ammonia was through the roof I use the API master test kit and the water in the tester is super dark green putting the ammonia at a ridiculous 8ppm. Nitrites at zero ppm and ph at 6.2. Ive done a 80% water change. Put a new filter in added cycling starter (Nitrifying bacteria). I still can't get the ammonia down and my nitrites are not moving still at zero. Its like I'm cycling a new tank again.

Is the bio gone what happened?

 

[Scottyhorse]

Yeah, if you weren't putting an ammonia source in there, the BB is going to be dead, and you will have to re-cycle the tank.

 

[blert]

Get the ammonia down to between 2-3 ppm. Test nitrite, nitrate and pH. Give it 24 hours and test all four again. Report back with the results.