I would think Apocyclops nauplii should be small enough for blenny larvae. Otherwise, you may have to try Pavocalanus nauplii. You will have to build a nauplii harvester. Unfortunately, there are so far none commercially available.
A rectangular tank may also not be ideal for more finicky larvae. Round tubs or Planktonkreisel tanks may give better results (try the tubs first as they are vastly cheaper than custom build Kreisel tanks.)
If they spawn regularly I would suggest trying to raise them and experiment with different feeds and tank configurations - that's pretty much the only way to figure out what the best way is. I did just that with my Amphiprion bicinctus and went from just 30 juvenile fish to a yield of several hundred in only 4 iterations.
As for the blenny sexing, the difference between males and females of this species is actually small but significant enough to sex them. With other blenny species, it is either very hard to tell the sexes apart or the differences are so vast that males and females look completely different. The latter case usually leads to the sad situation that only the more colorful and flashy males are collected while the rather dull-colored and camouflaged females are left behind. I just saw that last weekend at a local store. They had really nice sailfin barnacle blennies, but very obviously only males as the females have no sailfins.
A rectangular tank may also not be ideal for more finicky larvae. Round tubs or Planktonkreisel tanks may give better results (try the tubs first as they are vastly cheaper than custom build Kreisel tanks.)
If they spawn regularly I would suggest trying to raise them and experiment with different feeds and tank configurations - that's pretty much the only way to figure out what the best way is. I did just that with my Amphiprion bicinctus and went from just 30 juvenile fish to a yield of several hundred in only 4 iterations.
As for the blenny sexing, the difference between males and females of this species is actually small but significant enough to sex them. With other blenny species, it is either very hard to tell the sexes apart or the differences are so vast that males and females look completely different. The latter case usually leads to the sad situation that only the more colorful and flashy males are collected while the rather dull-colored and camouflaged females are left behind. I just saw that last weekend at a local store. They had really nice sailfin barnacle blennies, but very obviously only males as the females have no sailfins.