Questions About Water Pond Fish Care Questions About Water Pond Fish Care

Q. I live in Pennsylvania and have had a pond with goldfish going on 5 years. The pond is approx 10' x 12' and 18-24" deep, inhabiting about 30 fish of various sizes (2-5"). The only thing I do for winter is turn off the pump and put in my pond heater. I have had no problems ever - the fish have been very hardy.

This year was very cold in December - the pond froze over except at the heater location. This week there was warmer weather and the pond began to thaw. I began breaking up the ice and discovered at least 10 fish dead, mainly all the larger ones - the smaller fish are still alive. Any ideas of what happened? What should I do differently to get me through January and February?

A. If you fed them after the water temperature dropped below 50 degrees, you could have killed the fish. Fish do not digest well after the temperature drops. Food decays in their system and then sends bacteria into the bloodstream. The only way to know the water temperature is to monitor with a thermometer. Water should also be monitored to make sure there is no ammonia and nitrite in water. Ammonia settles at bottom of pond where fish are over the winter. Also, you may want to consider adding an airstone to increase the amound of oxygen in the pond.

Q. I have two koi about 10" in an outdoor pond and plan on putting them in a 75g tank for the winter here in Wisconsin. This is my first overwinter with koi. My question is, do they do well if the temperature drops below 40F? The garage is not heated. How often would they need to be fed if they are hibernating? I have a special "spring/autumn" food for a low protein diet. I also have a de-icer if I need to use it. Any suggestions would be appreciated.

A. Check with your local pond fish supplier for recommendations. If you have an area in your pond where water is 18" deep or deeper, fish will hibernate in that area. If the pond is not 18" deep, it's possible they could freeze.

You need to start feeding the spring & autumn food when the water temperature drops to 65 degrees and stop feeding when water reaches 42 degrees. It is not recommended that fish be moved to a kiddie pool or aquarium in a garage because this places the fish under stress from catching, transporting, and reacclimating. If you have no choice, you will need an aquarium air pump to keep the water oxygenated. Keep an eye on the water temperature. Feed infrequently, if at all. Check pH, nitrite and ammonia weekly. Water should be changed at the rate of about 20 percent per month. Cover with netting so fish do not jump out.

Q. This year I stated off with 5 koi and now I have 20. The large koi had babies - she may have had them this year or last - but now they are noticable and there are 15 of them. I really don't know what to do with them, but for now they don't seem to be bothering anything. I'm just thinking down the road if they live to get bigger, I really don't need to have 20 koi in my small pond. My question is, in the deep of winter, will the large koi eat the babies? Do large koi eat small koi if they are hungry?

A. The babies will be just fine. I just recently purchased a house with a small ~400 gallon pond established. We have three 16" Koi, eight 10" Koi, nine 6" Koi, about 20 1" Koi babies, and 25 .1" babies. The one-inch-ers were not there when we put the contract on the house. Thirty days later when we moved in, low and behold, lots of tiny koi - they were only .5" then. About two weeks ago I noticed one of the six-inch-ers was about to pop. Sure enough, the next day we had about 25 little tykes swimming around. The 16"-ers dont pay any attention to the babies. I think major pet stoes have a community tank where you can drop off extra fish.

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