I can only go by my two species experiences (three sets of hatchlings) and it turned out differently both times. With the mercs (dwarfs, O.mercatoris), I kept them in breeder nets until they were 5 months old. With the O.briareus, they were loose in the the 60+ gallon tanks from the time they hatched (I attempted to keep them in breeder nets but they refused to stay

). If you can keep them IN the breeder nets, it is much easier to be sure they are getting enough food. NO NEW HATCH BRINE. I had good luck with getting both species to eat cyclopees (frozen, not dried) using a pipette to feed (we just over fed the large tank but could target feed in the breeder nets). As they grew frozen PE mysis worked well as does freshly killed shore shrimp placed at the end of a pipette (they are too small for a normal feeding stick but you might be successful with an unpainted toothpick in a net but will need something longer if they are loose in the tank). This time around we found that removing hermits from their shells and feeding (a bit of a challenge) the whole animal was a big hit. The trick is extracting the smaller ones. I froze them to kill them and then used a hammer on the shell. Usually I came up with a feedable carcass but sometimes not and others silently called me names while trying

. If you go through my journal in the raising octos from eggs forum I detailed the feeding and who ate (to ad nausium I am sure but I will go back and reread it myself for reminders when I have another batch).
Because the survival rate is low (but bimacs seem to be higher than O.briareus from the few tries we have recorded), I would bring home at least 3 and as many as 5. You will have to be prepared to offer them for sale should you have success with more than one (you are pushing the limits of the 46 with one).
There are off and on discussions about flow rates for the hacthlings but my observation is that they needed it (I had a power head pushing water through the breeder nets except at feeding time). Tatanka lived inside the return pipe until he outgrew the holes and Cassy was always (and both still den) close to the Koralias. Even though a tiny octo can get into a Koralia, mine were uncovered (note that I would not do this with any other kind of power head). It does not mean that some may not have been sucked in (I never saw what happened to the 18 or so in Tatanka's tank) but Tatanka and Cassy survived with them this way.