Do you know much about fish tank filters? Do you know that fish tank filter is a must-have for any goldfish tank? Do you know why?
Well.. fish tank is an environment where there is a confined volume of water. Over time, physical and chemical wastes will accumulate and make the water dirty and toxic. This is even more so for a goldfish tank. Yes, goldfish are beautiful and graceful, but they are also very messy. They eat a lot and they poop a lot. So their tank can get dirty very quickly.
That’s why fish tank filters are very important. They are essential in providing filtration function to maintain the cleanliness and good quality of the water. What’s the point of goldfish keeping if you can’t see your goldfish through the dirty water or that you have sick or dead fish laying around, right?
Wouldn’t you rather enjoy a tank that is clear and where your goldfish are healthy and happy?
So knowing a little about fish tank filters and how they work will be helpful for you in getting one.
So what is there to know about fish tank filters?
For a start, there are 3 types of water filtration that should happen in your fish tank. They are:
- Mechanical Filtration
Mechanical filtration removes suspended particles such as excess fish food, fish poop, plants and debris from the water. The fish tank water is pushed through the filter media where the suspended particles will be trapped.
- Biological Filtration
Biological filtration makes use of nitrifying bacteria colonies to convert toxic chemical compounds such as Ammonia and Nitrite into non-toxic Nitrate. Please check out my post on Nitrogen Cycle for more details. These nitrifying bacteria colonies live and grow in the filter media.
- Chemical Filtration
Chemical filtration targets dissolved organic compounds and pollutants. The filter media work by attracting these contaminants and then absorbing or turning them into harmless compounds. A popular filter media for this is the activated carbon.
Not all fish tank filters are capable of doing mechanical, biological and chemical water filtration. Different types of fish tank filters may have different capabilities. Let’s check out the 5 common off-the-shelf ones for a goldfish tank.
5 common off-the-shelf filters for a goldfish tank
1. Sponge Filters
Sponge filters or air-driven filters are the most basic and cheapest filters available. You will need an air pump to get them to work. The suction power created by the air bubbles draw water into the sponge and trap physical wastes and debris. The sponge also provide the surface for those good nitrifying bacteria to colonize.
2. Hang on Back (HOB) Filters
HOB or power filters are external filters that hang at the back or the side of a fish tank. When turned on, the impeller will cause a suction mechanism which draw water up the inlet tube and into the filter compartment where the filter media are placed.
Physical wastes and debris get caught in these media which also serve as places for nitrifying bacteria to grow. Most of the time, filter media with activated carbon is included for chemical filtration. Filtered water will return to the tank via the filter outlet.
3. Canister Filters
Canister filters are external filters that can accommodate more filter media. This means that they can do a better filtration job and have the ability to handle larger volume of water. They need less maintenance as well.
Most of the time, canister filters come with filter media for mechanical, biological and chemical filtration. However if you would like to replace those with your preferred filter media or just to add on, you can easily do that with canister filters. Yes, they are really very flexible, but they don’t bend over backwards. 🙂
Canister filters draw the water in from one side, then push the water through the filter media to get to the filter outlet on the other side. Filtration happens as the water passed through the different layers of filter media. At the filter outlet, filtered water is pumped back into the tank.
4. Internal Filters
Internal filters are compact filters that are fully or partially submerged in the fish tank. Some basic ones work like sponge filters but with their filter media enclosed in a box or casing. Some have power heads or motor units to create suction of water into the filters. Water are then passed through the filter media and out from the filter’s outlet.
In many ways, they are like miniature version of canister filters which are placed in the fish tank. Due to their compact size, there is a limitation on how much filter media can be placed in the filter. Besides that, they also take up space in your fish tank.
5. Undergravel Filters
Undergravel filters consist of plastic grates and an uplift tube. These plastic grates are placed below the substrate in the fish tank and are connected to an uplift tube at one corner.
An airstone (which is connected to the air pump), or a power head is used to create suction in the uplift tube. If airstone is used for this purpose, it is placed at the bottom of the uplift tube. If power head is used instead, it is fitted at the top of the uplift tube.
When powered up, the suction in the uplift tube will draw the water in through the plastic grates to the tube. In this process, mechanical filtration happens as wastes and debris are pulled into the substrate and trapped there. The substrate provides a place for bacteria to grow, thus creating biological filtration.
Comparison of these 5 types of filters:
|Types of Water Filtration||Relative |
|Sponge Filters||Mechanical & Biological||Low||- Cheap|
- Easy to set up & maintain
- No chemical filtration
|HOB Filters||Mechanical, Biological & Chemical||Medium||- Easy to set up & maintain|
- Usually include chemical filtration
|- Can be noisy
- Limited space to add filter media
|Canister Filters||Mechanical, Biological & Chemical||High||- A lot of filter media can be added to provide better filtration|
- Can handle larger volume of water
- Troublesome to maintain
|Internal Filters||Mechanical, Biological & Chemical||Medium||- Cheaper than canister filters|
- Easy to set up
|- Limited space for filter media
- Take up space in fish tank
|Undergravel Filters||Mechanical &Biological||Low||- Cheap|
- Easy to set up
|- Very troublesome to maintain
- Not suitable for substrate diggers or sifters like goldfish
When buying a filter…
- Make sure that the filter is capable of handling the water volume of your fish tank. This information is available in the filter’s description or specification.
- Get one that can support all 3 types of water filtration, or at least has the flexibility to do so.
- Find one that goes with what you intend to show in your fish tank. If you think having a filter in the tank will spoil the layout, then get an external filter instead.
- Especially on more expensive filters, read up some reviews on the particular filter model and see whether it’s worth the money.
That’s all I have about fish tank filters. Hope this little bit of information helps!
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