A lot of people are modifying their needlewheel impellers by putting a mesh material over the needles. This is a very cheap, easy, and popular skimmer modification to perform, but many people don’t know the drawbacks to this mod. Deltec, who has a popular line of protein skimmer products, has been tinkering with meshwheel and needlewheels for 15 years. They have the following to say about the meshwheels:
As water enters the pump, the first thing that it comes into contact with is the mesh on the impeller. 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 impeller to impeller.
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 impeller 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 maximize 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 impeller 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.
So, think twice about the mods you want to perform on your aquarium equipment, and realize that for every gain in performance, you lose something else along the way.
Sources:
Deltec: Pinwheel vs Meshwheel
