Cleaning
In my experience, Gouldians are more susceptible to illnesses caused by poor environmental hygiene than other species of finches. I have noticed a direct correlation between the health status of my flock and the level of hygiene in their environment. I clean perches once per day, I change water twice daily and replace ground cover as needed to maintain a minimum of fecal buildup. It really does make a difference!
As a daily disinfectant I use grapefruit seed extract (GSE) at about twenty drops per cup of dish soap and simply place this on a wet towel or scrubber. GSE can be found in health food stores. It works as a substitute for bleach in terms of killing germs but is a non-toxic cleanser that is entirely safe to use around birds.