Yes the cube back will be painted or covered black and trying to figure out a grid for the bottom as to get equal tests for each light. Thinking of using some black pvc as depth risers as to ensure testing depth per section will be consistent.
A 48X24 tank would have been more consitent as some of these lights are mean to cover more than 24 inches and it would allow you have have extra data points concerning spread. The guys at BRS use a grid. I think a grid made of acrylic would do the job well.
something like
YOu could probably get a large piece of plexi cut it down to the tanks dimensions, route a grid on to it with a router going a few millimeters into the surface. Sick some rare earth magnets on the intersections you want to sample and have a magnet on the probe that stick to that magnet. The magnets would help with alignment and keep the positions consistent. YOu could also buy four acrylic rulers to set at each corner to set the different heights with out the worry for a level since all corners should be at the same measurement. An acrylic rod with magnets on both sides held by magnets on the outside of the tank could be used to hold the height.
Unless you are going to go with static points of measurements. I think the guys over at BRS TV have a rig they use, maybe it's worth shooting them an email see if you can get your hands on it or plans to make one. They use a 24x24 cube except when they are measuring lights meant to be wider than that.
We do have have a bunch of new 120g aquariums but they have the center brace and would make things difficult. I like the idea of using the magnets as a way of holding the probe down and would work even better if we used a devise like BRS does with pre drilled holes for the meter.
That is the what the big vats with tanks on top will be used for. In our case many frags from the same mother colony will be used along with some of the main mother colonies.
