Timid Red Scats

I have wanted some Red Scats for a couple years and finally bought three juveniles each about 3/4" in size yesterday. They seemed very healthy and active in the LFS and during their first day in my tank they were very busy swiming around, chasing each other and looking for food. This morning however, I woke to find all three of them hiding behind one of the powerheads in my tank and all of today they have spent hiding under a peice of driftwood. Is this behavior usual for young red scats, or is it likely an acclimatization issue or something bothering them?

Currently they're in fresh water, which is what the LFS had them in, I plan to slowly move to a brackish environment.

They're solo inhabitants of a well cycled 3ft x 1.5ft x 1.5ft tank which contains a small peice of well aged driftwood and a few plants (japanese rush).

Water parameters taken today.
PH: 8.0
Ammonia: nil detectable
Nitrite: nil detectable
Nitrate: less than 10ppm

Well it seems to have been an acclimatization issue, I guess they were just getting over the shock of being in a new home. They seem to be perfectly happy now, eating like little pigs and very active.