There are many different types of aquarium filtration. Mechanical, chemical, and biological filtration come to mind, and you can read about them at length in The Kick-Ass Aquarium.
In this Aquarium Care 101 post, however, I’ll go over the most important of the three primary filtration methods: biological filtration.
No filtration form is more efficient than biological filtration!
Biological filtration depends on the work done by a group of beneficial bacteria. These bacteria occur naturally in almost all bodies of water, and, most importantly, they consume fish waste.
What makes fish-waste harmful anyway?
Well, the fish poop itself is not the thing that causes potential problems in the home aquarium. Instead, it is the toxic compounds released by fish poop (and by other forms of decaying organic matter) that can make Aquarium Care a nightmare.
In particular, Ammonia, a substance that is highly toxic to all tropical fish, is readily released by fish poop. This toxic substance is also released by your tropical fish through the gills.
Ammonia is made up of one nitrogen and three hydrogen atoms. That’s why scientists abbreviate it as NH3. In other words, NH3 describes the chemical makeup of Ammonia.
In the home aquarium, Ammonia may also be released in the form NH4 (called Ammonium), which is not toxic to tropical fish.
Nevertheless, whether your fish release Ammonia or Ammonium depends on several factors, many of which (such as pH and temperature) are beyond the range of what most tropical fish will tolerate.
Ammonia can be removed by means other than biological filtration, but that’s doing things the expensive and hard way!
Those beneficial bacteria will do a lot of the work for you if you provide them with aquarium conditions that will allow them to thrive.
But, before I get ahead of myself, let me briefly describe how the beneficial bacteria remove Ammonia from your aquarium water.
There are two groups of beneficial bacteria, and they detoxify your aquarium in a two step process.
1) The first group of beneficial bacteria absorbs Ammonia and produces Nitrite as waste. Nitrite is also toxic to tropical fish, but, fortunately, the process does not end here.
2) The next group of beneficial bacteria absorbs Nitrite and produces Nitrate as waste. Nitrate is the relatively harmless end-product of biological filtration.
And, that’s it. That’s all there is to it!
So, how can you encourage these beneficial bacteria to grow in your aquarium?
The beneficial bacteria are not free swimming. That means that they need places in your aquarium to cling to. In other words, they must have a surface area on which they can grow and multiply.
These clingy bacteria homes most often include 1) filter material and 2) the sand or gravel at the bottom of your aquarium.
1) Canister filters are great at providing biological filtration. I pack my canister filters with bio-filtration media. This media looks like a bunch of highly porous blocks which provide the beneficial bacteria a lot of surface area.
My canister filters are, essentially, massive beneficial bacteria colonies!
2) The bottom material of your aquarium constitutes the largest surface area in your aquarium! The sand or gravel in your aquarium, therefore, houses the most abundant population of beneficial bacteria.
The subject of gravel type and biological filtration is a complex one, and you can refer to Chapters 4 and 8 of the book to learn about the ins and outs of proper substrate choice and care.
Basically, though, the larger the aquarium is, the more gravel or sand it will house. More gravel or sand, in turn, translates both to a larger surface area and to more beneficial poop-eating bacteria!
This is just one more reason why large aquariums are easier to care for than are their smaller counterparts.