I have an older version of the water fountains so it really doesn't hold a lot of water at all. T & P go through the water that's in there in less than 2 days. I've already come down on the second day to find the thing sucking air. I guess that's a good thing because it means they're drinking, but I'm amazed the thing is still working because I think it said to not let it run dry because it's bad for the motor.

Anyway, because they go through it so fast, I really only disassemble the entire thing for a good cleaning every 2 months or so. It has a charcoal filter on it, so when they do get food crumbs or other "floatables" in it, the filter usually does a good job cleaning it. I add fresh water just about everyday, so the water that's in there isn't getting "stale" at all.

I should probably do it more often, but like Amberlee says, when I do clean it, they don't seem to use it again for awhile. Just like as soon as I clean up the food they drop on the floor around their dishes they immediately drop more there so I think they prefer it that way.

Here's a picture of Tubby drinking out of it. As you can see, no resevoir at all.

And while I'm at it, here they are eating. Notice the one or two pieces of food on the floor. Guess this was right after I got done cleaning.