I use peat in my filter. It's not an instant solution, it's a mess to deal with, it will stain your water and lower your pH, but it seams to induce spawning IMO. I think it creates a much more natural water environment for the fish.
I like the tannins in the water and the fish and plants seem to also. I've got a 20 gal breeder with 3 roseus danios that are little fry machines (everytime I look in the tank theres more fry) and it didn't happen until i added a peat bag to the filter. You can buy peat filtration pellets, but I used 100% organic peat.
You will have to change out the peat about once a month, but I think I paid $12.94 for a HUGE bail of peat, so it won't break the bank.
I use R/O water on another set of tanks and it's a PITA. My R/O water comes out at a pH of about 3, so I have to buffer it with baking soda to get the pH to 6.8. The little 20gal has been going stable with a pH of 6.8 and fairly soft water, just by using the peat, for well over a year now.