Fish in small ponds with limited resources survive by adapting to the environment. They will adjust their behavior and feeding habits based on the available resources. Fish in small ponds will also compete for resources, and some may even resort to cannibalism to survive. Additionally, the population of fish in a small pond will be limited by the available resources. To maintain a healthy fish population in a small pond, it is important to manage the pond's resources carefully and avoid overstocking with fish.