[hahnmeister]

Removing the mesh on the wheels (unless you remove it all...lol) does very little to reduce the output of the pump if the pump is dealing with minimal back-pressure. Think about it... the rpm is the same, so the centrifugal force is the same, and so will be the angular acceleration.

On a single pass skimmer where the pump is under several inches of water (your typical cylinder shape), this places back pressure on the pump (which reduces its output). The impeller diameter makes an impact then because the water is trying to resist the pump more.

On these ATB's, esp the nano, the water level that the cone is in is so low, so back pressure on the air intake is minimal. Thanks to the cone shape, the waterline inside the body can be kept much lower inside the skimmer as well, so the back-pressure on the pump is minimal. So as long as there is a bare minimum of mesh on the wheel... putting more on doesnt do much.

If this was an ATI bubblemaster, Euroreef, etc... something where the water level in the skimmer was resisting the pump more, then yes, removing some mesh might make a difference. But with these cone skimmers... I figured it wouldnt work, and when Victor tried it, sure enough... no difference. The best way to cut back the pump is by placing a restriction on the output of the pump (since placing more restriction on the intake of the pump can lead to problems if you dont know exactly what you are doing). And sure enough, it worked.

Sometimes, reducing the mesh/impeller size in the volute can actually lead to more air intake since you just made more room in the pump to handle it.

The upside of the method Victor used to restrict the pump is that the pump is still able to process the air and water, and if anything, 'mix' it for a longer time than previous. It may not be noticable to the naked eye, but the bubbles coming out of the pump, even though they are lower in volume, are more than likely smaller in diameter... so its almost an even trade: the air output might be restricted by 32%, but I bet those bubbles are a good deal smaller as well, which increases performance because the net surface area of the air in the skimmer is boosted. Remember, two bubbles with the volume of one larger one have something like 50% more surface area between them (cant remember if thats the exact number or not... something like that... its late so I dont feel like doing the math).

Sometimes when an asperating pump has its throughput increased too much, the air doesnt spend enough time in the pump to get blended as well as it could be... we have seen this on other pumps like the ReefFlo Dart in the past where the water flow is so high compared to the air throughput, and the consequence is that the air spends much less time in the pump getting 'blended'. Sometimes a little less flow can make for a better mix.