Thanks for the detailed explaination NH! I'm repping you, which I don't do often!!
I think that grow store owner is a good guy to talk with and take advice from. It sounds like he hasn't given in to the "appeal" of fancy plug and play corporate produce item's and still likes to use his brain - plus pass that knowledge down to his customers. I think that it's great that your system is easy enough that your wife can care for it in your absence, and additionally, that she will do it for you. My wife doesn't know much about whats going on, but she does like to peek.
My design actually comes from making Koi ponds (filtration systems). Yes you can go out and buy things like drains, skimmers, sieves - but without a knowledge of how to make all the plumbing work intelligently, it all ends up failing. Also, I was taught by one of the industry's best, who promotes "home made" biological filters over commercial ones. The type of filters we make could be made commercially, however it would be foolish (for reasons I could explain if you were curious.
) My mentor worked in an oil refinery for over 30 years so he has a vast knowledge of how pumps and 'plumbing' systems work. He's the BEST. He has grown plants before inside of the filters, but more so just dropping net pots in and leaving them - not physically trying to grow good plants.
I'm still working on getting all of my ideas of paper. Perhaps someone in this thread, or maybe one of your friends on here will see it and maybe can help change design a bit. I'd love to see someone attempt to build it.
6 or 7 gal per day is a lot! Thats some great information, as when your running a contionous system that loss of water can shut you down!
Thanks NH your the best! I look forward to chatting and updates.