Yeah I set one up for a friend (who bought it without asking my advice). It hold less biomedia then a Eheim 2217 and I wasn't sold on the cartridge filter concept thinking it might clog up a lot. After a week running on his 150g cichlid tank he called me ...flow had dropped a lot. I went round and we changed out the cartridge (easy to do thank god) it was clogged solid.
The design of it isn't great ....too much water trying to be filtered through a cartridge with too little surface area .... its going to clog up a lot.
If you want to spend a lot of money on a top notch filter ...go buy a Eheim Pro 3.
The G6 is basically a gimmick wrapped in a marketing brochure .
Overpriced
Overhyped
Under performs ....