What kind of test kit are you using?
Are you sure the tank is cycled? You post it is from Christmas but you posted late January about starting up a 20L. When did you add the fish? Temp? What is your water change schedule? I suspect you have an ammonia spike and something is amiss with your testing.
I have a fishless cycle going on in a tank now that is is currently on day 31 and I still cannot add fish and I too used filter media from an established tank. amm 0, nitrite off scale, nitrate off scale. I should have the nitrite fall off any day now and then I do a water change and am done but it is not something that can be rushed. PH and temperature affect cycle times too.
Are you sure the tank is cycled? You post it is from Christmas but you posted late January about starting up a 20L. When did you add the fish? Temp? What is your water change schedule? I suspect you have an ammonia spike and something is amiss with your testing.
I have a fishless cycle going on in a tank now that is is currently on day 31 and I still cannot add fish and I too used filter media from an established tank. amm 0, nitrite off scale, nitrate off scale. I should have the nitrite fall off any day now and then I do a water change and am done but it is not something that can be rushed. PH and temperature affect cycle times too.