I need to know fish that can survive at about 72 degrees Fahrenheit in a pond ecosystem, and eat only plants, or can survive and be healthy on only plants. Fathead minnows don't work, they eat baby snails, and they tend to not be very healthy since they are bred as baitfish. It also needs to be able to survive in a small tank. No running water. All the oxygen is coming from plants and the air above the water. I know a lot about fish, but I'm stumped.
