I really like your inspiration for this tank> i watched the video you posted, i saw the tents and kayaks and I was like, ok, it's a really pretty picnic spot, but so what. and then I see the sinkhole! OMG. That is nuts.
I would put the YMCA wood behind the other one. It would be best I think if you had more tall ones like the two pointed one and just line them up. The YMCA one, although it has a lot of character, doesn't seem to mesh so far in my mind. I wish you didn't break the ymca one though
Wouldn't it be cool to have some ferns or whatnot protruding from the water on the wood? ANyway, very neat. I look forward to seeing how you utilize the height.