It's contradictory information; everywhere I read it says "be prepared to care for 500 fry", but you say that a 100% loss is a very real possibility :0( I thought it would be kindest to cull eggs rather than fry (and easier on me, emotionally).
I saw a "brine shrimp factory" for sale on the Drs. Foster & Smith website. It looked suspiciously like an up-turned soda bottle!
I wouldn't cull eggs as you might be culling out the only fertile ones, or be culling the best fish out of your entire spawn.
I would think it would be rare for a first time breeder to successfully raise 500 fry to maturity. 100-200 is more in the region I would expect for a larger spawn raised by a novice breeder.
Also, if your fish are new to it all, you may find you end up with a smaller spawn size anyway. Sometimes can take them a couple of spawnings before it all clicks. I have seen some pretty awkward embraces out of my virgins.
That BBS hatchery does look like a soda bottle just put onto some plastic stand. It's just as easy to make your own out of two soda bottles. There's a few Youtube tutorials floating around to look at.
Yes; culling eggs could be tossing my best fish, but I don't have the resources to handle 100+ fry to maturity. I want a modest # of adults (10-20), plus I'm assuming fewer fry would be easier to keep alive. Unless there are people who want fry to raise? I'm after a good yellow HM- my would-be parents are gorgeous.
You will find that you will naturally lose the weakest fry as you go along so that does help cull numbers down. Most first time pairs are probably not going to give you 500 fertilised eggs as their wrapping techniques are usually not perfect.
I would be hesitant to cull out eggs because while your pair is lovely, you don't know what genes they carry. You might end up with only 10% quality fry and the rest needing to be culled. But if you culled out a majority of the quality fry by destroying the eggs, you are going to end up with a spawn of mostly culls. I have seen some terrible fish come out of what appeared to be top notch pairs because those fish just did not nick well for some reason.
I would also be hesitant to mess around with the nest too much to get the eggs out as you might disturb your dad if he is particularly nervous.