Sunfish Pond was located between Madison and Lexington Avenues, and covered what is now Park Avenue, between 31st and 32nd Streets.
....a little lake called Sunfish Pond, which extended to Fourth Avenue and covered the site of the present car-stables. Sunfish Pond, Mines tells us, was famous for its eels, as well as sunfish and flounders. He adds that the brook which fed it was almost dry in summer, but in times of freshet overflowed its banks and spread from the northern line of the present Madison Square to Murray Hill, more than once compelling those who lived along its lower course to resort to boats as the only means of reaching the avenue. (From New York: Old & New: Its Story, Streets, and Landmarks; By Rufus Rockwell Wilson; J.B. Lippincott company, 1902)
Viele shows the pond in his famous water map,along with the stream that supplied it. The pond is approximately in the center of this crop.
A tighter crop of the area of the pond from Viele's map. I haven't been able to find any trace of this pond in the present New York-- is it completely gone?