I have bred blues also..... There is not just ONE thing to focus on. Its all about balance and keeping up with it.
Here is what i did.
Food: blood worms and New Spectrum pellets. Fed once a day, alternating food on days.
Temp: 70degrees F
Single large plant like Sword in pott
One pair per tank at least 20 gallons
Good water Aeration
Water changes every 4-5 days with a GOOD water conditioner... not the cheap stuff.
I have bred in hard water above ph7.8, but it is easier to breed in water less than that.
Use a sponge filter like what is found on the angels plus site
The best article i have ever found regarding this is on angelsplus