While cutting, the old filter setup got clogged just after a short time, so I replaced the paper filter and filter cartridges with a fleece filter.
The filter works in the way, that the water from the fish tank pump, from the DI filter and from the EDM machine flows to the 110mm tube in the middle of the filter. This tube is 300mm long and has a perforated 200x50mm surface at the bottom of it.
New fleece is guided from the new fleece roll along the bottom of the tube to the used fleece roll. The perforated surface is 100mm shorter than the tube and the fleece to give the fleece enough surface to seal against the tube left and right from the perforated surface, so that the water can not bypass the fleece.
When the fleece gets clogged, the water rises in the tube until a float switch turns on a motor, that motor pulls new fleece from the roll until the water level is low enough to turn off the motor again.
I tested the operation of the filter with granules from a DI filter and also while cutting some stuff, so it seems that the filter works better than the old filter setup.
Even though the filter has larger pores, it is able to keep the water clean / transparent all the time.
I also changed the tubing.
The pump for the DI filter and the pump that pumps the water to the electrode now have separate inlets.
So, with the new filter setup the system should be ready for longer testing operations.