I thought I remember reading something when I first got started into aquaria that had to do with this same basic effect. That author wanted to see why propellers instead of impellers are not being used. In conclusion, he basically found that the propeller design he had was inferior to just about any impeller based PH
on the market.
This is not so say this won't work. But I would like to see more independent reviews other than the one they have on their webpage.
, I was curious to see how much it was but their "order" page does not work)