I wish! I settled on a figure 8 for the coffee table in a 20L with a 206, almost zero maintenance even with daily feedings, however is brackish.
I believe Cory from Co-op is upgrading his 300g to a 600g for his fahaka. I have heard/read to expect that area, Puffers are powerful swimmers and when they choose to open their tail wide and go full force you defiantly want them to have more than the minimum room. I was blown away swimming with larger saltwater puffers in Hawaii. They would let me closer than any other fish and It was clear why. With a quarter flick of the tail and this fish was down 40 to 60 feet, seriously looked like it teleported compared to everything else in the water.