A device measures the high and low fluid levels of a fluid body. A housing has a shaft with a buoyant weight, the shaft protruding through a cap on the housing's top and capable of sliding through the cap. A first ring encompasses the shaft and is initially positioned immediately below the cap, while a second ring is positioned immediately above the cap. As fluid enters the housing, the shaft rises in lockstep with the fluid level causing the first ring to be pushed downwardly on the shaft and when the fluid level falls, the shaft falls causing the second ring to be pushed upwardly along the shaft. The distance between the rings is the amount of fluid level variation. A debris tube attached to the housing measures the upper limit of fluid level. Subtracting the amount of variation from this upper limit yields the lower fluid level limit.