A pond that is biologically balanced will practically take care of itself, whereas a pond that is overloaded with fish will forever be trouble.

Add the right amount of plants and get your filter working to handle the amount of waste created by it's inhabitants, and you'll have clear, pristine water. It really is that simple, but sometimes hard to achieve. Do not overfeed your fish, and don't overcrowd them. If your water is too messy, you may be guilty of one or both of these things. If you want more fish, then you need to increase filtration.

Also, adding plants greatly reduces the abundance of string and blanket algae by competing with it for nutrients. When your plants are growing well, your fish are happy and healthy, and your water is clear--you have balance!