your tank is smallish so you would be after Sepia bandensis. which grows about 6 inches long and would be a fit (tight) but a fit.
Sepia Officinalis do not require a chiller. they can exist at higher temps this just shortens their life span a bit. the biggest officinalis live in cold water and live about 24 months.
read this
http://www.tonmo.com/cephcare/cuttlefishcare.php
Before you Buy a Cuttlefish by Colin Dunlop
It will explain a great many things.
TONMO is your friend go there lots and read everything