Cycling With Established Filter Media


I am in the middle of cycling with established filter media. The media was from a small tank with a single betta who reached the end of his life. I am now trying to cycle a larger tank in preparation for getting more fish. I added ammonia and it has taken a couple of weeks but it has finally dropped to 0. I am going to add more today. My nitrites are also 0. Is this because they have not had time to build up, or is this because I already had some bacteria from the established media and it has been keeping up with the ammonia?

If I continue to add ammonia every time it drops to 0 and my nitrites remain at 0 and my nitrates are increasing, is that when I can be sure the tank has cycled?


Yes, when you have 0 ammonia, 0 nitrite, and some nitrate, you're cycled.

Here's what I'd do:

Add 2 PPM ammonia to the tank at a certain time, let's say 10 AM. Check your parameters the next day at 10 AM, and if they're 0 ammonia, 0 nitrite, and some nitrate, you're golden. If not, redose to 2 PPM and repeat. If you plan to add a lot of fish at once (let's say you're adding a schooling fish, or something really messy) do the same thing, but dose to 4 PPM.

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