A friend of mine is in the import/export business of fish and quite knowledgable.
He made me a 960 plywood tank out of line-x. The tank requires one more coat, drilling the overflows, and then inserting the glass (not much more to go). It would have stayed at his place for completion, but I had to transport it ahead of time due to contruction timelines on my addition.
Anyway, this was the first time he had made one, but apparently his friends in germany have been doing this for some time with products the same or similar. These tanks have been running for 20+ years.