Well... it appears that this attempt was a bust.
I didn't do a very good job at keeping an eye on salinity level. Usually when I have stand alone tanks, I make a line on the glass where the water level should be and then top off to that line. For some reason, I didn't do that this time and I was occasionally topping off with a fresh water drip, when it occurred to me to check. The salinity crept up to about 1.035ppm last week and I'm pretty sure it took a toll on the remaining larva. They were still alive, but didn't seem to be eating.
I'm going to make sure I do the line think next time around.