Lion Mom, et.al.,
I just set up a 5 gallon Hawkeye tank for someone...Here is the scoop: 5 gallon Hawkeye tank from Walmart, 25 Watt Hydor Theo Heater, Marina S-10 Slim Filter and of course decorations, substrate, Betta, their choice. This exact set up is very Betta friendly. Nice compact 9 Watt Florescent lighting and removable cover to protect bulb from condensation. The Marina S-10 Filter works great for this tank. It is a hang on back power filter. The extra nice feature about this filter is it is totally adjustable on the flow. Also included with the filter is an intake sponge. The only thing about this exact setup is you have to completely remove the canopy (lid) to take care of water change/maintenance. It is because of the length of the Marina Filter. The filter gets in the way when you try to open the lid. But, I do like the Marina Filter because it is totally adjustable on the water intake/output flow rate. Another nice feature about this filter is it does not require priming. Nice feature to have. Anyway....Now I can totally see why you really like the 5 Gallon Hawkeye tanks!!