Regardless of removing comments from the thread, the answer will still be no.
A 55 is okay for a pair of FM's and a few dithers. So once you move the O, and the GT out then you can put them in. They may well breed - but only if you get a male and female, which is always a challenge. They will need to be pretty much fully grown to protect the nest from a 9 inch O. And in a 55 with a GT and an O, the chances of breeding are minimal - as are that of the fry surviving. FM's are much more placid than GT's and most O's. So they may well become stressed and be attacked by the larger O. How large are the GT and the FM's?
I personally would leave them seperated until you get you're larger tank, it isn't worth the risk.