The 5 gallon looks like it sits on the plumbing itself, and that there is no other support. Is that right?
Both tanks are very impressive. I am not sure what gadgets you are running, but it would be interesting to see a walk through of both systems. I am fairly certain you have more equipment on your 15 gallon than i have in all all my tanks combined, and all of them are larger (125, 55, 29, 20).
I have always kept my aquariums simple, but these setups make me want to attempt something more high tech. I have to say that i am extremely impressed, and that you have done an amazing job on the tanks.