I am currently using a Pm rfca4 w/ effluent chamber on my 180. This model is rated for tanks to 200g. I am now upgrading to a 450g.
I have made the assumption that so long as my load/consumption of alkalinity and calcium do not change then I should be OK in using this reactor for a while.
No doubt within some period of time (since Ive got so much real estate now) I will be adding significantly more SPS. For the time being this wont happen, and it would appear based on current effluent and co2 rates that I have a significant margin of increased output available should I crank it up.