Where do you get the information that garlic is bad for birds? I’ve used it on dozens of my own, and have friends do the same. Never had a problem. Garlic also goes back centuries, before we had modern medicines, and it is extremely effective. I would go so far as to say safer than an otc...
Garlic, apple cider vinegar, chipotle powder, cinnamon, oregano. These all fight coccidia and are what I use. Per gallon I add two Tbs garlic and 1 acv, 1 tsp cinnamon, and a dash of oregano OR chipotle. Be careful with the last two, they’re potent.