Well, for whatever reason, the siphon on the tank went nuts last night, started sucking the overflow dry. I played around with the valve a few minutes before I left, but still not sure why. I 'think' that the siphon tube on the secondary drain came unstuck from the suction mount, drooped into the water, and magically became air tight (it was previously requiring some glue to seal it back up).
Something to consider this weekend.
Ammonia levels were back down to 0.7ish (I guess), so tossed in another 10cc and called it a day. Oh, and nitrite levels were up...a bit...0.1 the day before, I'd guess 0.125 or 0.15 now, slight increase. Should go up further once the plants are in.
Also, the auto top-off system stopped working, not sure why, have to investigate.
Still evaporating ~2 liters/day, so definitely have to take those measurements this weekend and get glass cut for the main tank. Princess Auto has a 0.25" glass bit ($4), so I can still have the siphon tube going into the tank off the secondary drain. Will need a grommet of some sort to allow for removal of the glass. Hm...actually...
Instead of two large squares (what the tank is designed to hold due to center brace), I can do four rectangles. Means I only need to lift one panel to do trimming/etc, and also means the piece with the siphon tube won't need to be moved all the time. This might also be a little cheaper.
To lift the glass, I'll just silicone on some acrylic handles. The lights are already on little legs, so will leave that be for now.
For the sump...I'm thinking of using the existing glass for the forward section (part that will be removed to access the filter, etc), and a framework with custom-cut rubber sheet to fit around the piping.