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Contents 1 About Filters 1.1 Mechanical 1.2 Biological 1.3 Chemical 2 How do Filters work? 3 Types of Filter 3.1 Internal Filters 3.1.1 Sponge Filter 3.1.2 Undergravel Filter ("UGF") 3.1.3 Internal Power Filter 3.2 External Filters 3.2.1 Canister Filter 3.2.2 Hang-on-the-Back Filter ("HOB") 3.2.3 Wet/Dry Trickle Filters 4 External Useful Links

[edit] About Filters

A filter is quite possibly the number one most important piece of equipment you will have in your aquarium. It provides constant (24/7) circulation throughout the tank, pull out any floating debris from the water column and will provide a home for the majority of the essential good nitrifying bacteria within the aquarium to keep the water parameters stable and removing the toxic waste produced like ammonia and nitrite.

See also Filtration FAQ.

The material held within the filter (called the media is split into three groups

[edit] Mechanical

This is usually a collection of lots of objects like balls or cylinders (or in the small filters, a coarse sponge) to try to capture and retain the larger pieces of fish waste or plant material so it can be broken down by bacteria over time.

The shapes create entrapment areas so causing a turbulent current which holds onto the larger pieces of mulm whilst allowing the water to pass through.

[edit] Biological

This is usually a sponge material which is either coarse or fine to hold nitrifying bacteria and to hold back medium to fine particles therefore helping to keep the aquarium water looking clear.

• Coarse sponges are not suppose to be changed very often as its large holes make it difficult to clog rapidly. You shouldn't need to replace this type of material more than once a year, if that. Simply take a bucket of aquarium water, place the coarse sponge in it and squeeze it repeatedly until it appears relatively clear of mulm.

• Fine sponges are designed to capture small particles of waste or decaying plant material and so often clog rapidly. They're not designed to be the main material holding nitrifying bacteria so they are taken out and rinsed clean often. Due to this repeated cleaning, they often lose their shape after a few months and need replacing.

• Specialised. This type of media allows extra biological action to take place. Typically these materials have a massive surface area compared to the ordinary material supplied with filters when you buy them. All this extra area allows much more aerobic (nitrifying) and anaerobic bacteria (which removes nitrate) to exist in your filter. This provides extra capacity to filter out toxins without having to buy a bigger filter.

Typical examples:

• Matrix by Seachem
• Eheim Substrat Pro
• JBL MicroMec
• Sintered or fritted glass material

[edit] Chemical

This is often special granules or larger shaped material designed to remove particular unwanted chemicals from the water. They will have a short lifespan and are often not designed to remain in the tank constantly. There are also additive materials which add certain chemicals to the tank in a slow manner.

Typical examples:

• Activated carbon - a black sponge or pellet material. Removes metals and other trace elements.
• Nitrate removers - a sponge or granule material. JBL ClearMec for example.
• Dissolved organic waste - cleans the water and increases the redox value. Purigen by Seachem for example.
• Additives - Adds a particular chemical to the water. Calcium or peat is common.
• Ammonia removers - these either absorb ammonia into the material or convert it to non-toxic form. JBL AmmoEX or Zeolite stones for example.
• Silicate removers
• Phosphate removers
• Algae inhibitors

[edit] How do Filters work?

They typically work in two ways.

You have a electrical pump which turns a propeller which ejects water from the top of the filter to the outlet which causes a vacuum and water is sucked up and passes through the material providing the filtering action.

The other type, usually referred to a sponge filter passes air into the back or base of the filter which causes a vacuum as the air rises and water is sucked in and passes through the material providing the filtering action.

[edit] Types of Filter

[edit] Internal Filters

Internal Filters are usually either situated in custom built housing within an aquarium or can be bought separately. They will be located below the waterline within the tank. They are best for smaller tanks, lightly stocked tanks and for smaller community fish.

[edit] Sponge Filter

Sponge filters work by using an air pump to create upwards water flow in the centre of the sponge. This causes water from around the sponge to be sucked into the filter where it is mechanically and biologically filtered. This type of filter is not considered effective on tanks larger then 5 US Gallons (18.9L)}. The most typical use for sponge filters is in breeding tanks, as fry are not likely be to killed if they are sucked into the sponge filter.

[edit] Undergravel Filter ("UGF")

Undergravel filtration is a fairly dated form of filtration and is not popular with experienced aquarists. It has a plastic slatted tray that sits at the bottom of the tank with substrate on top - this tray means that UGF's are not suitable for planted tanks nor sand or fine gravel substrates. One or more vertical pipes, called airlifts (or uplifts), are attached to the tray through which water is drawn using a powerhead or an airstone (powered by an airpump). This pulls dirt and grime down below the tray to the empty space underneath. This means that the filter functions both mechanically, by trapping debris, and biologically, by acting as a colonisation site for the bacteria that break down the waste.

Due to the fact that all the waste is effectively kept underneath this tray, it is difficult to have a truly clean tank, to clean this out the substrate and tray need be removed.

[edit] Internal Power Filter

Internal power filters are a good choice for smaller aquariums, although they can be an eyesore. They feature a pump at the top with the outflow, underneath is media in a detachable casing and the intake grill. They are available in various powers suitable for all tank sizes and are a compact way of filtering a tank.

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[edit] External Filters

These will be located outside the tank. They are often more powerful than internal filters and more desirable for larger tanks or tanks with messier inhabitants.

[edit] Canister Filter

[edit] Hang-on-the-Back Filter ("HOB")

[edit] Wet/Dry Trickle Filters

These work with an intake tube dropped down into the tank with a motor attached at the top, which should be half in and half out of the water. This tube will suck water out of the tank, through the media located along the top, and this will then trickle back down into the tank at the other end. These types of filters are usually found built into aquariums rather than bought off the shelf.

[edit] External Useful Links

• Choosing an Aquarium Filter by Practical Fishkeeping magazine
• FAQ on Undergravel Filters by Practical Fishkeeping magazine
• A Primer on Aquarium Filtration by Leo G. Morin, Ph.D - Seachem