Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Here are 4 ideas. The one at the bottom is the best, this is the way I do it.
If you can swap media, do it. The established tank can share up to 25% of the media in the filter, and not have problems with any mini-cycle. This may be roughly 1/8 of the bacteria in the system.
If you cannot share media, then put some of the new media in the established tank in a place with good water flow. No need to run the whole filter on the tank. I use a mesh bag for ceramic bio media, but you could also put a sponge in there, bacteria grow great on Aquaclear sponges.
If you want to run the new filter on the old tank, go for it. That is a lot of extra water movement, though.
With any of these 3 methods you only have a fixed amount of ammonia to grow bacteria. Whatever is being produced by the livestock in the established tank is all you have. You will not grow very much bacteria on the new filter media when there is already a filter that is handling all the waste just fine.
The best way to jump start the nitrogen cycle:
Put the new media in a 5 gallon bucket and set up an air bubbler or fountain pump. Add some decor (stones, driftwood, whatever you can take easily) from the established tank. Used filter media would be the best. Then add ammonia to the water in the bucket to test 5 ppm. Run this exactly like the fishless cycle and the new media will grow tons of bacteria really fast. You will get a lot more, a lot faster than running the new filter on the established tank because you are providing more ammonia and no competition from plants or established filter.