This is a walk-through of the basic techniques around aquarium filtration and how they apply to betta tanks.
This information also applies to community tanks of all kinds, but is more focused on freshwater than saltwater tanks.
Filtration is optional for a single betta bowl
If you have just one betta in a bowl or aquarium, you don’t need to get a filter. Personally, I don’t like the noise a filter adds, and one of the finest things about keeping a betta a bowl without a filter is the silence. If you skip the filter, though, you will need to stay on top of water changes. A two gallon bowl should have a complete water change every 7-10 days. Five gallon aquariums should have 50% of the water changed once a week.
When to get a filtration system
If you’ve got a community tank, you ought to get a filter. Also, if you’ve got a lot of plants in your aquarium, you may need to get a filter to keep up with the inevitable leaf shedding and decomposing that goes along with having plants.
Having a filtration system does not mean you can skip doing water changes. You should still be removing 20% of the water from the tank every week and replacing it with treated tap water.
Also, filters need to be cleaned out every week or so. If you do not thoroughly rinse out the filter sponges and/on “filter media” your filter pump will have to work much harder and you will shorten your filter’s lifespan by 50% or more. A good-quality filter, treated well, can last ten years or more. One that’s neglected may break in 9 months.
Types of filtration
There are three kinds of filtration: biological, mechanical and chemical.
Biological filtration works by making use of the “good” or nitrifying bacteria that break down fish wastes into nitrate and nitrite. Biological filtration works with (and basically, is) the nitrogen cycle you learned about in the section on cycling your tank. Biological filtration is used in just about every filter available right now. It requires a lot of surface area, so sponges and other porous materials are commonly used to maximize the bacterial action.
Mechanical filtration means actually pulling bits of waste and whatnot out of the water. Usually this is done by running water through a sponge. Actually, the sponge is performing both mechanical filtration by grabbing the particles, and biological filtration as the little bacteria that live in all the crevices of the sponge break down the captured particles.
Chemical filtration means the filter is removing dissolved compounds from the water. Most fish filters focus on biological and mechanical filtration; chemical filtration is used only sparingly. You are kind of using chemical filtration when you treat tap water with water conditioner to get the bad gases and heavy metals out.
The only time you’d really need chemical filtration after water treatment is if you wanted to add a bag of activated carbon to your filter to absorb odors, or if you had an ammonia problem and wanted to put a bag of “ammo rocks” or “ammo-lock” in your filter. There are also nitrate and nitrite absorbing “rocks” or granules that you can put into a plastic mesh bag and then put into your filter.
