After about two and a half weeks of using the three methods in post #20, I have removed thousands, the huge majority of which have been yellow. But still, probably half, or a little more of the thousands that remain are yellow.
Lately, I have been feeding them adult pellets (that I pulverize in a coffee grinder) and the blended frozen seafood mix. Gotta keep working the numbers down so they can grow. I've been able to keep the tobi in check. I don't think I have found any over 1.5" yet.
Here are some of the dark ones at 39 days old, most of which are in the 5/8" - 7/8" range. It's almost hard to believe that most of these soragoi looking things will turn into showa and utsuri.