A fish tank filter works by removing physical debris, breaking down harmful chemicals through biological filtration, and sometimes using chemical filtration to maintain a healthy aquatic environment.
Here's a breakdown of the typical filtration process:
The Three Stages of Aquarium Filtration
Most aquarium filters utilize three main types of filtration: mechanical, biological, and chemical.
1. Mechanical Filtration
- Purpose: Removes particulate matter such as uneaten food, plant debris, and fish waste.
- How it Works: Water passes through a filter media (e.g., sponge, floss, or filter pad) that traps the larger particles.
- Benefit: Keeps the water clear and prevents the buildup of these particles, which can decompose and pollute the tank. Regular cleaning or replacement of the mechanical filter media is essential to prevent it from becoming clogged and ineffective.
2. Biological Filtration
- Purpose: Converts harmful chemicals into less toxic substances.
- How it Works: Beneficial bacteria colonize the filter media (e.g., ceramic rings, bio-balls, or sponges). These bacteria convert ammonia (produced by fish waste) into nitrite and then into nitrate.
- The Nitrogen Cycle: Ammonia (NH3) -> Nitrite (NO2-) -> Nitrate (NO3-). Ammonia and nitrite are toxic to fish. Nitrate is much less toxic and is removed through water changes.
- Importance: This is the most important aspect of aquarium filtration. Without biological filtration, ammonia and nitrite would build up to lethal levels, poisoning the fish. It is crucial to allow the biological filter to establish fully when setting up a new tank ("cycling" the tank).
3. Chemical Filtration (Optional)
- Purpose: Removes specific pollutants from the water.
- How it Works: Various media are used depending on the pollutant being targeted. Common examples include activated carbon (removes odors, tannins, and medications), resins (remove phosphates, nitrates, or other specific chemicals), and ammonia removers.
- Usage: Chemical filtration is often used to address specific water quality problems or to maintain pristine water conditions. It is not always necessary for a healthy aquarium.
Types of Aquarium Filters
Different types of aquarium filters employ these three stages in various ways:
- Hang-on-back (HOB) Filters: Hang on the back of the aquarium and draw water up through a tube. They typically include mechanical, biological, and sometimes chemical filtration.
- Sponge Filters: Use a sponge as the primary filter media and an air pump to draw water through the sponge. Provide excellent biological filtration.
- Canister Filters: External filters that offer a large amount of filter media. Excellent for larger aquariums.
- Undergravel Filters (UGF): A plate is placed under the gravel substrate, and water is drawn through the gravel, which acts as a mechanical and biological filter. Less common now due to potential for detritus buildup.
- Internal Filters: Submersible filters that are placed inside the aquarium.
Maintaining Your Filter
Regular maintenance is crucial for a filter to function effectively:
- Cleaning/Replacing Mechanical Filter Media: Clean or replace regularly (weekly to bi-weekly) to prevent clogging.
- Rinsing Biological Filter Media: Rinse gently in used tank water during water changes to remove debris. Never rinse biological media with tap water, as chlorine will kill the beneficial bacteria. Only rinse when heavily soiled; excessive rinsing can disrupt the bacterial colonies.
- Replacing Chemical Filter Media: Replace according to the manufacturer's instructions.
- Water Changes: Regular partial water changes are essential to remove nitrates that accumulate as a byproduct of biological filtration.
In summary, a fish tank filter works through a combination of mechanical, biological, and sometimes chemical processes to remove debris and harmful substances, creating a healthy and sustainable environment for aquatic life. The biological filtration stage is the most crucial for maintaining a stable ecosystem within the aquarium.
