I think climate may play a role too. I fully agree with the above post by
, that my horses much prefer to drink out of a clean trough or bucket. But I have never, ever seen even a hint of algae in my horses' containers. Yet I've never once used bleach to clean them. Just straight water and a scrub brush (one meant for washing dishes).
The trough is not huge, so I can easily dump the water out, rinse, and refill every day. Same with buckets. They are scrubbed weekly, but emptied, rinsed and refilled daily. That seems to be enough. However, we don't get the intense heat that you would get in the southern US (I'm in Eastern Canada), so maybe that has something to do with it.
That said, I've seen many stables in the area where the water trough is full of algae, so it certainly will grow if left long enough! I think the mistake people make is that they get a really big one that is hard to empty and scrub. It gets quite disgusting. And I've seen many buckets that were just crusty.
Bottom line: you don't have to be anal, but a quick lookover will tell you if the buckets and pans need cleaning. Some horses are certainly more messy than others, and some climates may support more algae growth than others so you have to adapt your routine to your situation. And even if they look clean, a good scrub once a week is a good idea.