Changing outdoor pond water without a filter requires using a sump pump to draw out some dirty water and using a regular hose to displace the pond water. Change pond water to maintain an outdoor fish pond with instructions from a koi breeder and aquarium specialist in this free video on fish care.
Now if you would like to do a water change on this pond and you do not have a filter such as a rapid sand filter or a bead type filter that you can do a normal backwash on, you will need a pool hose and a sump pump. For this you go right ahead and attach the sump pump to the pool hose, take the pool hose, hold the pool hose and the sump pump together and try to get into the center of the pond. If the sump pump does not stand up, that's perfectly fine. You're basically doing a water change here, you're not draining the whole entire pond. You'll then want to go right ahead and take the pool hose and either put it inside a drain hole if you have a drain or you can actually go right ahead and put it on your lawn. It works as an excellent fertilizer. And we'll just need to plug it in. Now we're actually going right ahead and draining the pond of some of the old water right here. Once we're done draining to a certain point, we'll go right ahead and hookup our water garden hose and start refilling the water. To do this properly, you're going to want some non-iodized rock salt and dechlorinator such as AmQuel or Prime. This is AmQuel, this is a product that's typically available in any pet store or aquarium store. You can either use AmQuel or their sister product which is commonly referred to as NovAqua. NovAqua creates a nice slime coat for the external areas of the fish for the mucus membrane. It's very good especially if you're going to be doing a major water change because NovAqua will help with any kind of stress that the fish may suffer. In this instance we've only taken out maybe 200 gallons worth of water so we'll just go right ahead and pour in a little bit. You can also do this by the cap, you can right ahead and use one cap full for every 20 gallons.