Originally Posted by Crazyfish
I'm not so sure about "instantly" cycled. I think it still takes time for the tank to go through the cycle as the bacteria has to occupy all parts of the tank and not just the filter. Even if you take a filter from a cycled tank and place it into a new tank, there will most likely still be bacteria blooms as the bacteria will quickly multiply to occupy the space so there may even be some cloudy water periods. I would say anywhere from days to 2 weeks.
Instant, as long as you are aware of the bio load of the donor tank, as well as the new tank. A mature colony of nitrifying bacteria is capable of doubling every 20 hours, I go with 24 for a bit of a safety cushion & ease of math. I also never take more than 1/3, once again safety cushion. Having many tanks running, with many extra filters means having the ability to set up just about any size tank I like, and rest assured that it's instantly cycled. For someone new to this stick to the 24 hour & 1/3 deal, feed the tanks lightly for the next few days.
Originally Posted by jaysee
I've started a dozen tanks by instantly cycling them with seeded media. Never once have I had a bacteria bloom. It's really important to add enough seeded media to handle the bioload of the new tank, otherwise you will have a mini cycle. The bacteria does not need to colonize all the other places that it will colonize in order for the tank to be cycled. That's how lots of people operate their quarantine tanks.
Taking media from a 55 to seed a 15 gallon tank is easy. Seeding a 55 from a 15 is not as easy. Some common sense is needed when stocking a larger tank started with media from a smaller tank.
Jaysee is on the money with this, same thing I've been doing for years, shutting down & setting up tanks as the need arises. Having tanks with a few mature filters in each, most running for years, and knowing the nitrifying bacteria is capable of doubling every 24 hours means (common sense here) I can & do on a regular basis take a tank that has 10 angels, add 100 angels, and not have a problem.
The common sense part is a bit of math, some water changes, and knowing Prime will lock up ammonia & nitrite for 48 hours. This most likely isn't something a new fishkeeper would want to try, (more common sense) but it is something more advanced aquarists routinely accomplish. I have no problem cloning tanks, jaysee has no problem doing it, many many others do the same without an issue. Much of running an aquarium is understanding bacteria, and taking care of those bacteria.