Social fish, limnetic Paxton Lake sticklebacks gather in large numbers during the day, usually swimming close to the surface of the water in the littoral zone. To protect themselves from predators, they congregate where there is a lot of surface cover or in areas of tall vegetation. At night, however, the sticklebacks prefer the deeper, open waters of the limnetic zone. When they spawn, they choose open areas away from any form of cover.

Only 45 mm is length when fully mature, the limnetic Paxton Lake stickleback is a small, lean fish with an elongated body that tapers to a slender tail. The fish has lateral plates that provide some protection against predators, a narrow mouth and three dorsal spines. The lateral line on this fish is complete and positioned high on the sides. For reasons as yet unknown to scientists, a small number-about five percent-of limnetic Paxton Lake sticklebacks don't have pelvic girdles.