Pond Aquarium Filters
Anyone who wants to stock fish in a pond needs a pond aquarium filter. This may sound odd at first, since you don't need filters for lakes and rivers. The difference is that while most natural bodies of water connect to other bodies, making them open systems, your pond is a closed system with minimal natural water exchange. It's more like an aquarium than a lake.Sizing Your Filtration System
Before picking a filter, you need to determine the volume of the pond you are working with because everything else depends on how much water you have. As with any other aquarium filter, the first thing you need to do is pick your pump. The ideal pump should be able to move the entire volume of your pond through the filter every hour to hour-and-a-half. Try to avoid swimming pool pumps and instead go for a low pressure high volume model for maximum efficiency.Filter Types
There are three main types of pond external aquarium filter: mechanical, chemical, and biological. Mechanical filters are the simplest, just a screen to filter out debris like leaves and particles. You do have to clean them, but that is rarely difficult. Chemical filters are more common in indoor aquariums than ponds, but some people do use them as they keep the water clear. Biological filters are the most important for your fish, as they maintain the nitrogen cycle that prevents toxic ammonia build-up in your pond water. The good part is that once your biological filter is established, it should last indefinitely.Filter Installation
The most efficient filtration systems involve a submerged pump, as they generally run cooler and move more water. One thing to look into regardless of your pump placement is a canister aquarium filter. The advantage of a canister filter, especially a mechanical one, is that it is very easy to change or clean. Anything outside the water is always easier to work on.Ponds or Aquariums
Most people who want fish are fine with simply getting an aquarium and setting it up indoors. It's easier, and usually less expensive than having a pond. What an aquarium doesn't do is transform your personal landscape. For that, you need a pond.