Huh, I don't disinfect the sprouts before giving them to the bird's. Then again, I DON'T sprout them in a warm environment. Moist? Yes. But warm? I understand that plants (or baby seeds) like warmth, but bacteria and mold like it even more. After they've started sprouting, I often keep them in the fridge at night to slow down their growth and to help prevent mold and bacteria. Also, it isn't a bad idea to soak them in ACV for 5—10 minutes daily, or when they're first sprouting and prior to giving to your birds. You can also use food-grade hydrogen peroxide to disinfect them for several minutes, then rinse.
I think the problem comes from disinfecting too much. If you're constantly disinfecting the sprouts, you're going to eventually run into bacteria resistant to the disinfectant. Also, if your house is warm and humid, it's a breeding ground for mold and bacteria, greatly increasing the chance of sprouts becoming contaminated. Also, you should probably use RO rather than chlorinated water. I can't say for sure, but if you use chlorinated water, the bacteria that DOES manage to grow on the sprouts will probably be nasty, highly-resistant bacteria. RO water doesn't encourage bacterial resistance, and it also has the added benefit of not having minerals or nutrients in it that might encourage bacterial growth. Also, proper storage of seeds prior to sprouting is probably important, too.
Proper disinfection of seeds prior to sprouting is also important. It's not a bad idea to soak seeds in ACV for 15 minutes, thoroughly rinse, then soak them in pure water for however long the recommended soak time for said seeds is.
For some species, the consumption of seeds and sprouts isn't all that important. However, for granivorous species such as budgies, seeds and grains (sprouted or unsprouted) seem to be a necessity. I know with my budgies, they become agitated and are reluctant to eat nutritious foods such as birdie bread, veggies, and pellets, if I don't provide them with some seeds and/or grains. It doesn't have to be a lot of seed/sprouts, just enough to satisfy their instincts (they can make up as little as a fifth of their diet). Sprouts are definitely a good option for birds with a strong drive to consume seeds, as they're more easily digested and healthier. An alternative to feeding sprouts is to collect fresh, not fully ripe grass seeds from pollution-, pesticide-, fertilizer-, and dog poop-free areas. It provides excellent enrichment, allowing them to perform natural foraging behaviours as they remove the tender, unripe seeds from the grass stalks. You can also provide fully grass stalk-ripened seed, but I also like to give them the stuff that hasn't quite finished ripening as this is the seed they would eat in the wild (many seeds and nuts are consumed prior to ripening).
