sponges are really really flow dependant. even with my generic crap sponges that are around all the time, if I change the flow in any way, a bunch disappear and regrow later elsewhere.
I have not had too many hitcher sponges keep growing, but many hitcher sponges that have started up elsewhere after the original fizzled because of flow or exposure to air or whatever.
and hence the permanent, albeit dynamic sponge population I now have.
I would never, ever, ever, buy a sponge from the LFS (...again

)
they are low percentage at best.
I guess what I'm saying, is don't bum out too bad if it fizzles, it probably will because it grew somewhere else in a different environment
ps, this is why SPS frags are the best vs colonies. that frag will grow into a colony that has adapted to its flow, vs trying to shoehorn a large colony into different flows and expect all the branches to do as well as when it grew TO the currents.