I would recommend this product By Tonyintn on 2/4/2014
Tonyintn would recommend this product to a friend
I have used this unit for almost 3 years on my 120g and it has worked perfect. If you hear the excess co2 pass as the the other reviewer described it is a well know fact that all you need to do to correct the problems reverse the clear and blue lines at the top of the unit to correct the problem.
I have used 3 calcium reactor sand for the price this one has done just as we'll or better in most cases as unit costing 2 times the price.
As for sound after reversing lines it's the same as all other units. For the value it's well worth the price.