In this section, I am going to talk about two of the three major types of filters. The three types are biological, mechanical and chemical. I will not talk about chemical filters in much detail. Chemical filters convert fish waste to nontoxic by-products by the use of chemicals, typically zeolite. In a pond set-up, this is usually not practical due to the size of the pond when compared to aquariums. Therefore, I will go into some detail about the other two types of filters. Earlier I discussed different types of filter media. However, it doesn't matter what type of media you use if the filter is not designed properly. An improperly designed filter will not allow the media to work up to its potential. In FILTER MEDIA I said that up to forty percent of the biological filtration in a pond takes place in the PVC pipe and tubing going to and from the filter. At that time, I indicated I would explain why this is possible considering the relatively small surface area of the inside of the pipes.

The answer is fairly simple. Inside the piping and tubing, the conditions are ideal for bacteria to grow and thrive. There is a constant supply of food for the bacteria and a constant supply of oxygen. The bacteria are continuously exposed to a fresh supply of water. The older, weaker bacteria is washed away thus the bacteria is always young and strong and is able to do more work and adjust to conditions faster. The insides of pipes have a small surface area compared to the surface area in a biological filter. Yet the bacteria in the pipe can do more work than the average biological filter. This is because the average biological filter is very inefficient. That is the point of this discussion.

I don't care what type of filter you put on your pond, if it is not designed correctly it is a waste of time and money. What is meant by "designed correctly"? If most of the biological media is performing under the same conditions as the inside of the pipe example, then the filter can perform up to its maximum potential. If the biological filter is sized correctly for the waste being produced in the pond and turn over rate in the pond is correct, then you have ideal biological conditions. At this point the percentage of biological filtering being done by the piping drops down as compared to the total filtering being done. This is the way it should be.