Rod, if you take the time to properly word your posts and spell check it will be much easier for us to follow your train of thought...
If your 140 gal is mature, meaning the fish have been in it for a while, the filters have been on it for a while and there has been no signs of ammonia or nitrite...
Then you can add the FX5 with no concerns... there is enough bacteria in the system to handle the current load...
If you remove one of the four filters from the mature 140 gal and replace it with the FX5... the three mature filters and the rest of the system will have almost enough bacteria to handle the full stock of the tank, and the little bit extra that is needed will reproduce itself in a timely fashion. Doing this will not require you to add any "old media" to the "new filter"... But if it makes you feel better you can…
If you wish to remove all four of the filters from the 140 gal, this will be removing a large quantity of the bacteria from your system. In this situation I would suggest putting some "old media" into the FX5. When seeding a new filter, it is best to put the "old media" in the first media chamber. This is so when clumps of bacteria break off of the "old media", it can move further into the filter and become lodged on the "new media"...
Anytime you do anything that may disrupt your bacteria colonies, it’s a good idea to monitor water quality closely and do water changes to keep ammonia/nitrite as low as possible.
