Sometimes you are lucky enough to see the egg transfer.
First, the female should get fatter than normal, and after the transfer she will again be normal, at least until she develops a load of eggs again.
The male will have a fuller pouch that will increasingly get fatter until the birthing, after which, if the female is again ready, he may accept another transfer of eggs the same day as the birthing. Often while pregnant, the male becomes reclusive.
HOWEVER, males tend to inflate their pouches with water as a sign to the female that he is ready and willing to mate.
If the pouch is inflated and the seahorse is floating then you have pouch emphysema, often because of deteriorating water conditions even if it looks great.