In all actualality, most spawns don't top 150, from what I have seen so far. Just let them do their business, and leave the male in a little longer, and/or cull the ones that are disfigured, missing fins, and/or have developmental issues.
Basically, you have to figure this. The average spawn I see is about 80, but lets be generous and say 100. So, you start out with 100 eggs, but only 90 get fertilized, so the male eats the 10 that are infertile. Then, out of the 90 eggs, say only 80 hatch, and due to fungus, being a "bad" egg, ect, 10 die off as well. Next, out of the 80 fry, only 75 develop to free swimming, then some of the larger fry decide their siblings are yummy looking, and you end up with 60, and so on and so on until you get a sizable spawn. I think you get the picture ;)