Nice!! do you mind if I ask how much you paid? I want to build an 8' long acrylic in the future.
Looks like a good build, interested to see how it comes out, imo the castors will deform over time so you won't be able to move the tank, I think you need to find away of taking the weight off them when the tank is full. I have seen solid metal wheels flatten at the bottom if they haven't moved in along time.