I assume your location is Melbourne, FL. If this is so, the fish you have are Fundulus seminolis, the Seminole killifish. These fish get very large and thick. We caught some on a boat ramp in Lake Eustis once that were about 8 inches long and a silver dollar body thickness. We thought we had a school of pickerel when we were bringing them up until we realized that pickerel don't school. They are a very cool fish, and will do great in an aquarium, but they will need some space to roam and a tight fitting cover to keep them from jumping out.