Aquariums: What tank size does a single adult Giant Gourami need?

I currently have a 3 year old Giant gourami that has been living in a 5 foot aquarium. He is healthy and active, but I know this species grows very large and produces a lot of waste as it matures.

I’m planning to build a custom aquarium specifically for him, and I want to make sure the size is appropriate for a single adult specimen long term. I would appreciate advice from experienced keepers about the minimum tank dimensions (length, width, height) that would realistically work for an adult Giant Gourami.

If anyone here keeps one or has upgraded their setup before, I’d also like to know what tank size worked well for you, and whether a very large aquarium is enough or if an indoor pond setup is usually the better option. Any suggestions on filtration and layout would also be helpful. 🐟