Well this weekend was cool...went out and picked up a free 75g tank. I am going to add some baffles and make a new sump for my tank. The one I use now is only a 55g and its really skinny..I don't really like it that much, at least on the 90g. Now I will have to disconnect this filter and possibly remove it all together when it is time to upgrade.
This sounds like the end of the cyanobacterial scrubber, but it is not. In fact, I cannot see how well it works without taking it out to see the difference. I will not discard any water besides what I shake off rocks/equipment in during upgrade. Essentially it will be no different than a water change. The new sump will hold 2x the water with the new design, so about 50 total sump gallons.