Well, just installed two 6025 nanostreams in the 50g aquarium.
This was the setup BEFORE the Tunze powerheads:
Seio 1500
Fluval 303 (for carbon and surface aggitation)
Deltec MCE 600, which actually has a decent amount of flow for a HOB skimmer.
The two 6025 replaces the Seio and the Fluval 303 canister.
The flow is now slightly greater and definitely more diverse.
It's actually quite amazing - if you place your hand in front of the Nanostreams it doesn't feel as strong as the Seio 1500, but it does just as good a job for flow.
Installation was quite easy, although you have to take some precaution as the plastics are thinner than standard powerheads. Definitely take seriously the warning of placing the two magnets close to each other. If they are within a few inches of each other they will snap together and you'll have a h&ll of a time trying to get them apart. Don't use this product if you have a pacemaker
With 3/8 of an inch of glass between them, it's no problem.
Start-up was almost immediate. If you hear some clanking on start-up, disconnect the power and try connecting again. It shouldn't take more than a couple of tries to get it running in the correct flow direction.
Noise-wise it's a bit louder than the Seio 1500 which is very quiet, even more so for it's size.
IMHO, two 6025 is enough for a 50 gallon aquarium. In conjunction with the Deltec skimmer, total flow and coverage is almost perfect. I have about 65 lbs of live rock.
We will see how this product fairs in the long run.
Cheers.