AQUARIUM FILTRATION

Author: Warren Stillwell
Date: October 31 2001

There have been many articles written about filtration. Most describe the different types of filtration only. The following information is designed to help you decide which is the best filter for your aquarium. Also covered will be materials and construction methods that work well and cheaply. A new approach to aquarium filtration will be discussed that has probably not been seen before. The article due to its size will be split into multiple sections. This first section will cover filtration methods only, as an introduction to the available filter types. Part 2 covers the importance of mechanical filters, how bacterial filtration works and what the best types of bacterial media are. Part 3 covers chemical filtration.

Filtration Methods:

There are five main types of filter system commonly used:

Undergravel - A porous plate below the gravel with uplift pipes using air uplift or powerheads to move the water through the gravel.
Box - A plastic or similar container that lives inside the aquarium that circulates water though some type of media using the air uplift method.
External - An external box that sits off the side or back of the aquarium. Usually powered, circulates the water through some type of media and sometimes has a bio-wheel.
Canister - An external container with pump and hoses that sucks water out of the aquarium, passes it through some types of media in the canister, then returns the water back to the aquarium.
Wet/Dry - A canister or box that either lives above the aquarium with a pump that sucks water out of the aquarium into the filter and flows by gravity back to the aquarium, or below the aquarium using gravity and overflow from the aquarium to the filter and a pump to return the water to the aquarium. The water passes through some types of media in the process.

Filtration Types:

There are three main filtration types:

Mechanical - Media that removes large water-born detritus and particulate type matter from the water.
Biological - Bacterial removal / conversion of dissolved toxic waste by-products.
Chemical - Media that removes dissolved chemicals from the water by chemical exchange.

These filter types will be described in parts 2 and 3.

Purpose of a Filter:

Fundamental to the success of a healthy aquarium is the stable aquarium environment made possible by scheduled water changes and filtration. Water changes provide systematic removal of wastes not normally removed by filtration and restoration of a balanced ionic environment. No system exists, despite irresponsible or misinformed claims to the contrary, that can replace water changes.

What a filter will do is keep the aquarium environment stable for longer so that water changes need only be made periodically. The time between water changes and the size of the water change will depend entirely on the size of the aquarium, the quantity and size of the occupants, how densely planted the aquarium is and the quality of the filtration system.

The next section describes more fully how each filter works, its associated costs and advantages and disadvantages.

Improvements:

There is a major improvement to be made to the canister filter and the trickle filter. The other types of filter cannot use the improvement due to their construction and the fact they do not have a powerful enough water pump.
By fitting a prefilter to the canister and trickle filter it is possible to extend the useful life of the biological media. Most advanced biological media manufacturers recommend the media is partially replaced every six to twelve months. If a suitable prefilter is fitted, the particulate matter that clogs the biological media is removed. Therefore the media does not clog and can be used for many years before replacement is required.
An added bonus is the ease of replacing and cleaning the prefilter. There is another major benefit, the organic matter that would normally decompose in the filter for up to a month can easily be removed every few days. The result is less build up of waste products the filter has to process, and the water stays fresher for longer. If water changes are still done regularly the quality of the water will be much higher promoting excellent fish health and happiness. The fish will breed more easily and have healthier fry. Disease risk will be greatly reduced when water quality is high.
The type of filter best suited for a prefilter is the pleated cartridge filter used on swimming pools. The cartridge and housing can be purchased complete and is fitted between the pump and filter, or tank outlet and filter. If used on a canister filter another pump must be fitted prior to the cartridge filter, as the canister filter’s pump will not be strong enough on its own.
These filters are very easy to change and clean. Simply hosing the cartridge every few days will keep it clean enough. Every 2-3 weeks the cartridge can be emersed in a weak solution of bleach to bring it back to new condition. The cartridge is then rinsed thoroughly and left to dry.
The pleated cartridge filter has a typical pore size of 15 microns. This is very small, and will remove all particles that will block biological media. The result is very clean water in the aquarium and much happier fish. Pleated cartridge filters come in many different sizes. A suitable size for cartridge filters is; 1000L/H 12sq feet, 3000L/H 30sq feet, 6000L/H 50sq feet, 12000L/H 75sq feet.
The cartridges have a square feet measure (being a US design) and the above mentioned sizes will ensure that standard aquarium pumps will work. If a smaller cartridge is chosen there will be too much back pressure on the pump resulting in reduced water flow.

Part 2 will look in depth at how biological media works. This will serve as a guide to chose the most suitable media for your application.

Data Sources / Acknowledgements

Discus Health Dieter Untergasser ISBN: 0-86622-168-9
Seachem: Seagram Data Sheets
Davies Pumps: Technical Data Sheet
Spa Pumps: Technical Data Sheet
Marine Invertebrates: Martyn Haywood / Sue Wells ISBN 1-56465-139-8