Hello kennybellew,
I understand why you designed it the way you did, but personalty I think the bottom tote is completely unnecessary. It has been my experience that if I wanted to move a water culture system it takes no time at all to disconnect the air line from the pump to move the reservoir. Then moving the air pump separately is so easy to do, there's simply no need (or even desire) to move both together. Also when you move it, it will be to heavy to do without removing (at least most) of the water first anyway, as well as probably the lid with the plants if they are larger than lettuce plants. So adding the cumbersome bottom tote just adds to the problem trying to move it all at once. Trying to move the whole thing mid grow at once will likely need two people to do effectively.

Also with only supports at the sides, the weight of the upper tote full of water will likely eventuality bow out the bottom without a center support. And with the two 2x4's sitting up on edge like that, they will likely fall over to the flat side when you move it. Unless your very careful moving it, and don't allow any water to slosh as you do (taking two people to do) unless you remove the water first. Laying down the 2x4's on the flat side, and stacking them would be much better support (but I would still want a center support).

Then there's the issue with the air pump. First the whole idea is to aerate the water with fresh air. The one small air hole you made to get the electrical cord through the bottom tote, may or may not be enough to allow enough outside fresh air to circulate to the air pump. If it dosen't then you will reduce the air bubbles you get, and eventually burn out the air pump. I wouldn't connect the pumps two air output lines, but rather use two lines and air stones for a more even distribution of the air bubbles. Lastly the salts in the nutrient solution will eventually/shortly clog the one way check valve, reducing and even completely stopping air from getting to the air stones. You can completely eliminate the need for the check valve in the first place if you keep/set the air pump about a foot or so above the water line in the reservoir. Then even when the power shuts off the water wont be able to get back to the air pump, and there wont be a check valve to clog.

Thanks for the feedback. I'll keep an eye on those things.