It's great to hear so many success stories with undergravel filters. I thought I'd have the constant, lingering possibility that 1-2 years from now, everything in my tank dies one night because the crap collecting in the substrate crossed some tipping point, throwing the water parameters all out of wack. But I think cleaning/redoing the tank once every 6 years is more than reasonable. I'd probably do one every year or so.
I'm thinking that by adding earthworms (who will digest the buildup and maintain it as soil), in conjunction with the beneficial bacteria, and what the roots of the plants extract, there won't be a need to ever clean the soil. Does that sound plausible?
55 gallon shrimp tank. Artificially selecting shrimp for hardiness, blueness, and fertility.