Welcome mayflower! Your designs resemble some of my final designs at you sound like your at the point I said heck with it, let's get started and see how it goes! I am operating with two 55 gal drums with liners so the drilling wasn't an option for me and without worry one tank would over flow while the other drained I opted for two separate systems. This has it's benefits as well as it's downfalls... More heaters, air diffusers, and tell water pumps instead of one as well as the biggie... The larger the water ecosystem, the more stable it is... Meaning if your patient and set it up allowing ample time to cycle, there are little to no growing pains... However with them separate, I'm able to have a gravel ebb and flow gb as well as raft system tank I plan on using as a nursery for babies... Good luck!! Looks like your ready to get your hands dirty! I'd love to send pics but I haven't read all faqs yet and just learned how to post. I know... Shame on me! Best wishes from southern Indiana!