Other research indicate that food rich is fatty acids (found in many live food including worms) increase the number of fry per drop. I personally saw an increase of at least 50% in the number of fry my females dropped after I started feeding them live BBS daily.

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GUPPY STRAINS I'M BREEDING:

Blue Grass
Blue Grass Swallow
Metal Blue Grass Swallow
Red Grass
Red Grass Swallow
Neon Blue Giessen/Ribbon
Japan Blue Blue Grass
Japan Blue Wild
Neon Blue

Strains I developed in my fish room:

HB Yellow (own line)
Platinum Pink Blue
HB Blue Leopard
HB Leopard Multi
HB Red Crowntail