I also have an opinion on water. It is a great medium for occasional therapies such as gut conditioners (apple cider vinegar, garlic), wormers, coccidia remedies and stress-aids but I use them occasionally, not permanently. Permanent additives imo are not needed if diets are balanced.
Perhaps some ground waters have different minerals which are palatable to some species but again, if the diet is complete, there's no need to add them.
The original question related to using an antibiotic-style chemical permanently in water to stave off water "going bad". Personally, I would look at a different approach because
-I am uncertain of the long-term effects of these chemicals on our birds,
-developed resistance by microbes to overly-used chemicals is a proven risk and
-to me, feeding and watering our birds is an important daily conection to them and trying to avoid this with chemicals is a little lazy.
Setting up an automated watering system for cages is no more difficult than for aviaries. Using external baths, drilling holes top and bottom, using polytube to feed water in through the top, wider pipes out the bottom feeding into a drainpipe or spoon drain. Timers are available and once or twice a day run the timer for a few minutes will clear the water replacing it totally with fresh.
Perhaps this topic could be started by someone with some pictures to help
In summary, fresh unadulterated water is surely the best imo. Occasional additives are part of general management. Permanent Virkon s to me is a bit too radical and has its risks.
Cheers
Tom