The Effect of a Waterfall Bypass on Water Temperatures in Koi Ponds
IAAAM Archive
Julius M. Tepper
Long Island Fish Hospital
Shirley, NY, USA


After several weeks of unseasonable air temperatures in Oct. and Nov. 2005, characterized by first very low, followed by very high temperatures, a study was conducted using data from client records seen during that time period. Water temperatures were recorded during pond calls, and through personal communications during this time period. These were graphed using markers indicating those that had a waterfall bypass installed (all morning visits) or morning visits with no bypass or afternoon visits with no bypass. Beginning on 11/3 and intermittently until 11/18, the author recorded the water temperature of his pond. Based on these readings, a trend line was drawn and extended back to Oct.1. All the ponds using a waterfall bypass had temperatures clustered around the trend line. Ponds without bypasses had water temperatures of greater variability, with morning temperatures generally lower than, and afternoon temperatures generally higher than, the trend line. Of interest were Clients J and L, who reported considerable swings in pond water temperatures over a short time span.

Besides the stressful effects of varying water temperatures on koi, the traditional practice of cessation of feeding in the fall, in regions that experience below freezing temperatures during the winter, is governed by water temperatures dropping below 50°F (10°C). This year, for those pond keepers whose ponds were not equipped with waterfall bypasses, this led to great confusion as temperatures first dropped below that point very early in the season and then rebounded with unseasonably high temperatures later in the season.

Although not currently supplied with most commercial pond filtration-circulation packages sold, a waterfall bypass can be easily fabricated and installed in almost all new and existing systems. It is recommended that for ponds in areas that experience below freezing winter temperatures, the waterfall be bypassed when water temperatures drop below 60°F (16°C).

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Julius M. Tepper, DVM

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