07-14-2009, 10:22 AM
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I don't know how many fish are in the 55g tank but I would certainly not transfer all of them at once. Moving the filter media from the 55g to the 130g will provide a bacteria population for the 130g but only what is in the filter media. Most of the nitrosomonas and nitrospira bacteria in an aquarium reside on surfaces within the tank (substrate, walls, plants, wood, rocks). The bacteria population in the tank is at the level of the fish in the tank, i.e., sufficient to handle the regular ammonia and nitrite levels produced by the fish. When you move the fish to the new tank, the bacteria in the new tank will only be at the level currently in the filter media you transfer and this will not be adequate for the ammonia and nitrite produced if all the fish are moved over at once.
One suggestion would be to move the filter media and some of the fish, leaving some in the 55g; new media in that filter will have no more effect on the fish left than the media transferred to the new tank, since the bacteria in the 55g will still be there. Under optimum conditions, nitrosomonas bacteria can multiply (divide by binary division) every 7 hours and nitrospira every 11 hours, although more realistically it is probably closer to 20-24 hours. All species of the nitrobactyeraceae have limited tolerance ranges and are very sensitive to pH, dissolved oxygen levels, salt, temperature and chemicals. Assuming the water parameters between the two tanks may be different in one or more of these aspects, some of the bacteria may die when transferred.
There is no shortcut to nature's methods. And ensuring the best health of our fish is our first priority.