If you left water in the other filters, I would lightly rinse them out with dechlorinated water before using. If they're canisters and closed, I'd be more aggressive about rinsing, since that's a long time to deprive beneficial bacteria of oxygen. You may have an anaerobic thing going on in there that's converting nitrate back to nitrite. You don't want that water going into a tank of fish. If they're HOB filters, then the water would have taken in oxygen to some extent and I"d just rinse a bit (dechlorinated water) so as not to remove any bacteria that may still be there.
Whatever filter has been running currently to sustain the fish should be able to continue once it's moved to the tank, even if it's only temporarily. Leave it on for at least 3-4 weeks to give the other filters time to get re-established. Add the substrate, feed lightly, and monitor ammonia and nitrite levels for a couple of weeks.
Bottom line, no one can tell you for sure how much nitrifying bacteria may still reside in the filters, so I'd just do all I could to ensure survival of any that may still be there. Can't hurt to try.
Whatever filter has been running currently to sustain the fish should be able to continue once it's moved to the tank, even if it's only temporarily. Leave it on for at least 3-4 weeks to give the other filters time to get re-established. Add the substrate, feed lightly, and monitor ammonia and nitrite levels for a couple of weeks.
Bottom line, no one can tell you for sure how much nitrifying bacteria may still reside in the filters, so I'd just do all I could to ensure survival of any that may still be there. Can't hurt to try.
