Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Think of it this way:
No matter how many tanks you have, or how many filters, you only have X amount of fish.
The bacteria to handle the waste of these fish will not increase in population just because you add another filter. Some bacteria will grow in the new filter, but then there is a bit less in the old filter.
When you take off that filter you are removing some of the bacteria that were processing the waste from those fish. Watch out for ammonia spikes from that donor tank.
Here are 2 ways I have done this:
1) Take no more than 25% of the filter media from a well cycled tank and put this in the filter of a new tank. Then do the fishless cycle to build from that beginning.
2) Split an established tank like this:
Old tank: Keeps all its hardscape and plants, but donated the entire filter. Half the fish go, too. This tank gets the new filter.
New tank: Gets all new hardscape and plants, but gets the well established filter. It gets half the fish.
Then both tanks are monitored and populations are built up as the plants and bacteria establish themselves.
a) Do the fishless cycle on all the new tanks without any starter media.
b) Add Nitrospira species of bacteria to the new tanks. Read the ingredients on the bottled bacteria products. If it does not include Nitrospira do not waste your money. Depending on how much you add this could be an instant cycle, or you could dose less and grow out the population with the fishless cycle.
c) Share some media from the established tank and dose it also with Nitrospira to make up for the bacteria you have taken.
d) Plant REALLY HEAVILY and stock moderately. If the plants hit the ground running they will be all the bio filtration a new tank needs. They will bring in some bacteria on their leaves, stems and roots, and the plants themselves will remove a significant amount of ammonia. Gotta make sure the plants are really growing well, though.