I'm going to do the pour method. Not sure on brand yet. I've used West Systems for all my other composite work (I'm a closet composites geek) but it's expensive at this volume, so I might look for a cheaper alternative. There are a couple internet mailorder places that have cheap house brands, and I know at least a few wood tank guys have used some of those with success.
reefman, the consensus from the ply tank experts is that marine ply is an unnecessary extra for something like this, and it's really expensive anyways. I ended up with oak hardwood ply. It's going to be a bit of a shame to cover all that nice oak up, but leaving it exposed doesn't really fit into my aesthetic design for the system.