I spent some time on CAD working out a revised design, and along with a couple ideas from others on RC I solidified a re-design last week. Over the weekend, my Dad and I built this new 2-piece ATS box that will replace the old one:
It has a frame for holding the lights made out of black acrylic, and the standoffs will be held in place on the outside versus the inside, that way the screw heads are out of the way. It also has a black strip that acts as a light blocker to keep light from getting around the reflectors better. I left the ends open for ventilation, I will probably add fans on one end of each side. The inner box has black on the bottom and sides, also to block light to the sump and outside of the device.
The inner box will house the screen, it is watertight and has holes drilled in the corners that match up with open sections in the base for drain tube connections.
Instead of going with modified (hacksawed) bulkheads like in my original design, I came up with a more compact and flexible design, I used a combination of a male/female screw-on PVC
connector (for 1" pipe) and rubber sink faucet o-rings, then used a table router to custom cut the hole so that it tightens down and provides a perfect watertight fit
There are 2 of these, one in each corner of the box. The screen will actually hang down to within 1/2" of the bottom of the box, and since the drain is off to the side and 1" above the bottom, the water will not cascade down and directly into the drain.
My idea here is that this will:
1) reduce or drastically eliminate microbubbles
2) reduce the chance of clogging or the pipe (which has not happened, but other have experienced it)
3) allow option of different heights of internal tubing to control the water level in the box.
Allowing the screen to become completely flooded provides for 3D growth of the algae (like I am seeing at the very bottom of the current design) and having a 2nd drain 1/2 way up the box would allow for buildup of algae and a secondary maximum water level. I considered cutting a slot out of one side of the box as an emergency measure, but that can be added later if it seems to be needed. I don't think it will.
I obviously have to add all the light fixtures and wiring, but should have it up and running in the new box by this weekend.