I updated the original post to reflect the changes in equipment and additional livestock acquisitions.
One issue I've encountered is that so much epoxy was used on this small water volume build, there is quite a bit of residue leaching or out-gassing into the water column and being collected by the skimmer. It finally seems to be slowing a bit, I'll do a few more water changes in the hope it totally dissipates.
I also need to increase the size of the heater as our offices are on a programmable thermostats that let things get quite chilly overnight. That coupled with the large percentage of surface area and lots water movement / evaporative cooling, 50 watts isn't quite enough to keep up.