Before every body gets too excited and starts exchanging their Deltec pinwheel impellors for the 'new ' mesh type impellors, I thought people may be interested in some information regarding the mesh wheel.
Deltec use the same mesh material in various applications and experimented with the mesh wheel impellor about 15 years ago, so this idea is not new.
The small diameter of the mesh does produce very fine bubbles as it cuts through the air however there are also a number of disadvantages of this material which is why Deltec chose not to develop it further in a serious commercial product range.
As water enters the pump, the first thing that it comes into contact with is the mesh on the impellor. Any algae or detritus entering the pump can easily become trapped within the mesh where it will start to build up requiring regular maintenance - a thing that most people like to think that they do, but in reality do not. As detritus builds up in the mesh the ability to split the air and therefore the performance will drop.
The mesh by the nature of the material is totally non uniform in construction so no two mesh wheels are the same which can lead to differences in performance from impellor to impellor.
With its non uniform shape it is almost impossible to balance which becomes even worse when there is any detritus lodged in it. An unbalanced impellor will oscillate which creates irritating vibration noise and the possibility of wear on the ceramic shaft and bearings which reduces the life of the pump.
A protein skimmer is about adding the maximum amount of air into the maximum amount of water to maximise fractionation and waste removal.
It was found that for all the mesh will draw air and smash it in to fine bubbles; the mesh wheel impellor draws far less water through the pump than a pinwheel. This means that you get lots of air but clean less water. The reduced water can even cause the pump itself to run hot and trip out the internal thermal switch.
The mesh material itself has a limited life span in salt water and will start to break down over time, especially in the turbulent conditions of the pump housing with potential for becoming trapped inside the pump. As the mesh starts to break down the efficiency of the skimmer will once again start to fall.