Jestersix

Is This Tank Cycled?

MolaMola

Supporting Member
Small jellyfish tank with rocky media bacteria filter and foam sediment filter set up about a year, continuously operating and getting periodic water changes and brown algae film wiping. Has not had living jellies in it for 5 months, so I wondered if the bacteria population has remained or has starved. So, on a Thursday we added 1/2 cube of frozen mysis shrimp and students started measuring ammonia, nitrite and nitrate. No ammonia reading on Friday, so I added 1/2 cube more and it went to 1ppm. On Monday there was no Ammonia or Nitrite, and Nitrate was like 5. Since then all readings have been 0. Would you say this tank is cycled and is ready for stocking?
 
Tank is cycled and has been for awhile now. The bacteria population is still there since it doesn't disappear as long as your tank hasn't been left dry the entire time. The fact that you were able to add 1/2 cube of food and did not detect any ammonia is a sign of that. You pulled an ammonia reading after the other half cube because there's not enough bacteria to process it all at once since it's been fallow for the last 5 months. I'd imagine that the ammonia was processed through the cycle even before Monday.

Just go slow with stocking the tank and you should be fine.
 
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