I have 3 Tunze Nanostreams kicking around and they are absolutely the poorest quality products I have ever purchased for an aquarium in the last 10 years.
All of them (including the subsequent replacements) have had the shaft in the motor block that holds the impeller in place break loose (that's 6 broken nanostreams if you're keeping count). This means the entire motor block needs to be replaced. I've given up on having them replaced under warranty and now have 3 broken nanostreams I need to just throw away but for some reason I keep them around and they mock me every time I see them
. Of course I went through the whole broken clips debacle several times as well. Not to mention one of the magnet mounts had a flaw in the epoxy that allowed water to leak in to the magnet causing it to swell and completely rust out until I discovered it.
My Voretech hasn't been without a couple minor problems but it is considerably more reliable. I would suggest forgetting about Tunze and going with a couple Vortechs if the budget will allow it.