Sorry I don't know of any detailed plans. Your idea goes with a post I had about insulating any unviewed tank sides, back, and the underside to lower heating costs (slightly). I apologize if I'm stating what you have already considered
. It's a neat idea!
Most commercial systems I have peeked at have pressurized water supply output to each tank coupled with an overflow system. A DIY system, especially if you want energy-efficiency, probably would need to use a siphon system between tanks with a final overflow into a sump at one end of the system. How are you planning on filtering? A large wet/dry? If you have different size tanks, you'll possibly have water current issues if there is a constant flow through all tanks in a series. High flow in small tanks, low flow in the larger ones. You'll have an increase in heat loss (through the added plumbing) so if you live in a colder area, you'll want to insulate the hoses. You still may end up running the heater(s) more since the smaller tanks have more surface area/volume for heat loss and your linked larger tanks will tend to cool more rapidly than if they were not linked together.
The only significant downsides I see, other than possible "spaghetti" plumbing all over the room!(!) is the same problem modern fish stores (recirculating water) have versus the old mom and pop pet shops (individual tanks). ALL the water is shared and if any disease gets introduced, you could spend more on medicating all that water than you'd spend on electricity. The other major worry is a clog in the system, depending on how you design it, could flood your room.
A gas generator would cost you a fortune to run. I'd bet it would take a long time to break even on electricity costs with the purchase cost of a solar panel or wind turbine.
Welcome to the forum!