As the weather gets cold so does your pond and you need to keep your koi safe. As temps start dropping – cut back on feeding and once water temps are 50 degrees or lower you should stop feeding – perhaps a light feeding on a warm day when it is sunny.
Use netting over your pond through fall and get the leaves out of there. Leaves will breakdown and can be toxic to the koi when the ice traps in the harmful gases.
In the summer months the bottom of your pond stays cool and the top is warmer from the sun. In the winter the opposite occurs. That being said it is better to keep that warmth in the pond. To help keep that warmth you should move your submersible pump up from the very bottom of the pond leaving at least 1 – 2 feet undisturbed. This will help keep that warmer water available on the bottom for the fish. Then once it gets real cold, go ahead and turn off the pump and falls & plug in your aerator. Your filter won’t be working, but without the fish feeding & with the water temps low there is little need to filter. You are better off retaining the heat in the pond and providing oxygen from an aerator. Likewise, don’t put the aerator on the very bottom – keep it at least 1-2′ off the bottom.
If you don’t use an aerator then certainly use a heater \ de-icer. You must allow the toxic gases in the pond to escape through the ice – if not your koi may get sick & could likely die.

If your pond is extremely shallow and you get very cold weather and thick ice, you may need to consider wintering you koi in a remote tank elsewhere.

You may also want to read a previous post about preparing you pump for winter.

Related posts:

1. Fall – Falling – Fallen – Get Ready for Winter
2. Spring Clean-Up… Done Right!
3. Is your pond going yet?

Aeration is the single best improvement you can do for a pond or lake & your fish – plus a diffuser system is also your winter de-icer to protect your fish from winter kill where deadly gases can’t get through the ice and the toxins kill your fish. So…. use a diffuser system and perhaps you can run it for free for life!

Windmills ar every effective – that is why our parents, grand parent and great grand parents and generations before them used them. Sure then came electricity – cheap, plenty of it etc… but we all know how that has changed.

Windmills won’t work in every application, but with 3+ MPH winds you can aerate your pond for free. We have windmills ranging from 9′ tall for water gardens and larger ones up to 25 feet tall for large ponds and lakes.  Our large windmills are capable of producing up to 3 CFM (cubic feet per minute of air) with a 9 MPH wind &  5 CFM with a 15 MPH wind – these are incredible numbers!

So if you are in a location where you can harness the wind – go for it! 

Related posts:

1. Aeration Pond Tips to Maximize the Potential of Your Pond
2. Help Keep your Koi Safe this Winter
3. Pond Froze? It’s not too late to do something about it.