I routinely use muriatic acid for mine. Don't use it for the impellers - it can easily destroy the magnets. It won't hurt anything plastic at all.
What I do is this:
Fill a 5g bucket just enough to almost cover your largest item with tap water. WEARING EYE PROTECTION AND GLOVES, AND PREFERABLY OUTSIDE, add a quart or so of muriatic acid to the bucket. Carefully submerse the item to be cleaned. There will be lots of foaming and nasty fumes - hence the need to do it OUTSIDE! Allow it to soak for 5-10 minutes or until the foaming stops. Still wearing GLOVES AND EYE PROTECTION, carefully remove the item and rinse it well in tap water - RO/DI is just a waste of perfectly good water. Set the item aside and proceed with the rest of the things that need to be cleaned. If the acid solution is strong enough, you won't have to wipe anything - it will all be magically dissolved!
Now comes time to dispose of the acid water - to neutralize it, slowly pour in baking soda until the foaming stops. You now have a solution with a ~ neutral pH, so dump it someplace (a storm drain works well for this)
I don't have the patience or the time to waste for the vinegar route to work. Not that it won't, but I don't really care to be tied up doing tank maintenance all day long.
hth
DID I MENTION EYE PROTECTION AND GLOVES???