Just to add to this, as I have an AM1000 reactor just set up today, and this could be important to others. The flow restriction is actually worse than that. The holes in the AM1000 reactor at the entry and exit point are significantly less diameter than the UP inline diffuser. So not only does this restrict flow more, as well as the bioballs inside, but the additional volume of water in the chamber also creates a flow restriction it seems. I have taken the bioballs out and still get a flow restriction.
When I ran the UP inline diffuser (albeit not very well as my reg was not man enough and am in the process of sorting this) there was no determinable flow change (I have a fluval G6 filter and this shows flow rate. With the Up inline running there was no reduction of the flow indicator). When I put the AM1000 on with the bioballs in I had 40% flow loss !!! Now I have it running with nothing in and I still get 20 to 25% flow loss !!!.
As soon as I can get my reg working properly with the UP inline I will be running that again.
