68 is far too cold for a betta. Fish are cold-blooded creatures, which means that their metabolisms are driven by the temperature of their environment. A betta kept at 68 degrees will be lethargic and will have a compromised immune system, making it much more susceptible to disease.
A 1 gallon container is not big enough to house more than just the betta alone, and any sort of algae eating fish aside from an Oto catfish is going to need a larger tank. The two most common "algae eaters" are common plecostomus and Chinese algae eaters. Neither is appropriate for your tank, as the plecostomus will grow to over a foot in length and produce a massive amount of waste while the Chinese algae eater will get to six inches or more in length and terrorize the betta.