As far as top viewing fish goes, Sarrasa comets, very colorful and easy to keep.
My 110 gal stock tank is the patio tub I started with in year 2000.
I run a Pondmaster submersible pump and filter.
12" square filter w dual elements (nylon and charcoal activiaited).
Pumps at 500 gph on this tub, can divert the fountain head to an underwater discharge partially or completely with a valve adjustment.
I add a Petco 9901 air pump with a large air stone on the opposite side from the pump discharge, for good measure (helps keeep the water moving too).
Bare bottom - no gravel.
When the water temps are consitently above 50 deg F at night I toss in some water hyacinth for algae control, water clarity, Comets eat the roots to add to their diet.
Throw in a water change and a 1/3 bottom vacuuum two or othree times a month and you have happy and healthy fish. I siphon the water straight into the flowerbeds.
Entire set up is outside and NO heat needed in my area of So. California.
Good Luck.