One thing of note. Sweet potato will make your water more cloudy if you leave it in too long. So plop it in one evening, and take it back out the next morning... happy feeding!
I sometimes feed raw sweet potato to my plecs (BNs and a royal). Sadly, one potato is still too much, and goes bad before I've fed it all to them. I cut it into reasonable sized slices and just plop a slice in. One really nice thing about it is that, unlike zucchini, the raw pieces sink on their own.