One male betta is still pretty entertaining. They're very interactive fish and love attention. If you are going to plant the tank, a group of kuhli loaches will do pretty well with the betta. They like a bit of cover in the form of plants and a coconut cave to hide from the betta if he's too curious but besides that, the conditions they require are similar to those for bettas and they co-exist pretty happily together. They'll mop any leftovers from the betta and once settled, you'll see them flying around the tank, certainly out for food. They can and will outlive numerous betta fish though if the tank is well maintained.