When dealing with tall tanks, treat them the same way you would the equivalent shorter tank. The reason being that the surface area is the same. So, if you wouldn't put them in a 20H you wouldn't put them in a 30SH (Show or Super High).
On a side note, I had that very same tank that I kept my octopus in and she laid eggs which subsequently hatched out. Best experience bar none that I've had in 35 years of keeping fish.