Pond Heater Temperature for Pennsylvania Koi Pond

2,500-gal pond, 2.5-ft deep, 6 koi, 2 goldfish, 2 catfish in South Central PA. Asks heater setting and whether to keep fish active all winter.

UK vs. US Practice

UK keeper heats to 18–20°C (64–68°F) for winter feeding. Author (MD) does not heat; uses de-icer only. Heating large pond extremely expensive.

Recommendation

Set heater/de-icer to prevent freezing only (~34–35°F). Let fish hibernate naturally. 2.5-ft depth is marginal for PA; ensure de-icer and aeration.