Originally Posted by audifusion
If I do a long tank it'd be a max of 6ish feet I length , I'd like to have at least 2ft depth and 18" height would be ideal.
Thinking of a center overflow
If you are displaying corals and fish for people in, and out of the hobby, like relatives, I don't think they will appreciate a tank that shallow. I would go 21". I just bought a 105 rimless and it's 21". Perfect for reaching the bottom.
Here's an old acrylic tank of mine. It was 8' x 24" x 17" tall. Awesome for corals, but not so awesome for fish. Most of the viewing was done top down.