Do Comline pumps suck in air without filter material?

[Christian J]

Will the supplied pump suck in air if you run a Comline without filter material? I used to do this with the old horizontal Tunze Quick-change filter (the one from the 1980s) and without filter material a vortex was formed in the filter box, pulling lots of air into the pump. I could stop the vortex from forming by placing a square piece of plastic diagonally inside the filter box instead of a filter bell (at least when using a Turbelle 1001 as pump, while a Turbelle 2002 was so strong that air got sucked in anyway). Would such a "plastic piece fix" work in a Comline filter too, especially considering the osmolator sensors are mounted in there? Is the fix even necessary? Compared with my old horizontal filter the Comline seems to contain a much taller water column, on the other hand its Turbelle 1605 seems stronger than my old Turbelle 1001.

To make matters worse my plans include both a Nano Wavebox and a Comline being mounted on the side glass of the tank, where the Wavebox waves are at their highest, so I fear the Comline pump will suck in air every time a wave drops below the Comline's surface overflow edge - or are the vertical water inlets underneath the Comline able to compensate for that fluctuation?

Why use a Comline without filter material, you ask? Simply because of the surface overflow...

 

[rvitko]

At home I use a 3167 Comline filter on my 210 plant tank, I use an older 3000/2 pump to run it. Occasionally the filters get clogged and I don't have time to change them immediately so I just pull out the filter bells completely and I don't get any bubbles, however this does dramatically drop the water level in the box and activate the osmolator.

Without the filter bells I think the wavebox could make enough disturbance that there could be bubbles, you will have to try it. I might suggest as an alternative, just using 0800.014 coarse sponge or a 870 media basket filled with carbon or another media you like to use to slow the flow a bit.