I use a DIY CO2 reactor and connect it to my Eheim 2217.
Because I don't like putting a pump into the tank.
But the opening of the reactor is bigger than the 2217's.
So I think there is not much back pressure created,
compared to the small opening of the AM1000.
Hi. I have a AM1000 and also an Eheim 2217. CO2 is so important in the system that I didn't want to have it relying on the flow through the Eheim, which of course becomes progressively worse as the filter starts to clog. So, I purchased a seperate external pump (an Aqua Medic Ocean Runner OR-2500). As this is an external pump I simply mounted it underneath my cabinet right next to the AM1000 and have a good constant flow through the AM1000 at all times. Works great!