Fish Tank Filtration and You: A Foundation to Your Healthy Tank

Happy fish, happy life. You didn’t buy a fish tank full of lovely fish just to watch them live a mediocre life, did you? I didn’t think so. I’m sure you know that you need filtration for your tank. However, there’s a lot more than just purchasing a filter.

You have to make sure you hit the trifecta of filtration needs. There’s a lot that goes into it and one might wonder why and how it got so complicated. Jeeze, they are just a fish in some water, right? That’s where you’re wrong.

Your tank is a tiny ecosystem that needs to be in balance or you can run into a whole host of problems. No one likes cleaning out a filthy tank, so let’s figure out how to keep it clean and keep your fish healthy.

How Does Fish Tank Filtration Work?

Well, it’s not rocket science but it does take some explaining. Filtration in your tank is a multi-stage process. You have to think that most of these fish or underwater critters you have purchased would be in a much larger area if they were out in the wild.

Since they are in a smaller tank, there is not enough natural filtration that takes place in that small space. So, you need to create some filtration via a few different channels to keep your fish and other underwater pals happy and healthy.

Filtration of your tank boils down to removing excess waste from the water. You want to decontaminate without getting rid of the healthy bacteria your tank establishes. There’s a happy medium that needs to take place and this can be accomplished by the combination of biological filtration, chemical filtration, and mechanical filtration.

Biological Filtration

Biological filtration for your fish tank is, hands down, the most important step of filtration. This is an absolute necessity and can be disastrous if you don’t get it right. The other forms of filtration we are going to review might not be necessary if you get this part right and your tank is small enough.


You may think of bacteria as the bad guy in almost every situation. In your fish tank, you need it! Why in the world do you need bacteria might you ask? Great question!

Good bacteria breaks down ammonia and nitrites in your tank. You have probably heard that ammonia is your worst enemy in a fish tank, and you aren’t far off.  That good bacteria converts the icky stuff in your tank into compound nitrate. This is much better for your fish and therefore your tank.

There are a lot of easy ways to promote good bacteria in your tank. One of the easiest methods is to have some kind of medium in your tank. A medium could be some fun colored gravel to make your tank look festive or even just some sand. The bacteria needs something to attach to other than just the fish tank wall.

Also, you really need to make sure to set up your tank properly from the get go. You can’t just fill a bowl up with tap water and plop your fishy friends in. Setting up a proper biological environment for your fish is fundamental in keeping your tank happy.


Did you think all of those little bubbles in a fish tank were for fish entertainment or visual pleasure for you? While they may be just that, more importantly, those bubbles are adding oxygen back into the water for your fish. Not only do the fish need an oxygen rich water environment, but so does that beautiful good bacteria.

There are a few ways to add oxygen to the water at an increased rate so our good bacteria can grow to take care of the ammonia and nitrites. Getting a surface agitator or bubbler in your tank is so easy, inexpensive, and very effective. It puts oxygen in the water at a faster rate and even helps “stir” your tank so you are filtrating properly.

Mechanical Filtration

If you have a tank bigger than a small glass bowl, I bet you own a fish tank filter. Most people think of a mechanical filter when they think of fish tank filtration. That’s all well and fine as long as you realize you still need to have the biological component.

So, what does a mechanical filter do? Basically, it hooks onto your tank wall and pulls the water through a sort of strainer. This strainer is going to pick up those particles floating around in your tank. Whether it be waste, food, pieces of plant, or your nephew’s sticker he dropped in, that filter will nab it.

The benefit to this is that it will grab those pieces of debris before they break down into ammonia or any other harmful chemicals for your fish. It also works as a gentle stirrer in your tank. This will allow it to sweep your water clean.

Another wonderful benefit to a mechanical filter is that it usually provides some aeration as well. This takes care of your oxygen issue in your tank. Just make sure you read up on how much it is going to help with your oxygen as well as for how big of tank it is for so you don’t over or underestimate it’s capabilities.

Now, there are a LOT of different filters out on the market. Some of them work just fine and some are worthless pieces of plastic. Choose wisely and do your research before purchasing the right one for your tank.  See our articles and reviews here.

Chemical Filtration

I’m not a huge fan of adding chemicals to your tank, but in some cases it’s just plain necessary. Chemical filtration is the act of adding a chemical to your filter to purify the water. More often than not, you are going to be using activated charcoal for this.

The activated charcoal is going to get rid of all of the particles whether they be waste, food, or pieces of plant that have decomposed in your tank. If you are having trouble with creating the optimal environment for a biological filter and mechanical filter, the chemical filter is a natural next step.

One of the most common times to use chemical filtration is when you are setting your tank up. Chemical filtration can accelerate the biological process so you are ready to roll with your new fish that much sooner.  Another time you would need to use chemical filtration is if you needed to use a medication for your fish. After that time period is over, chemical filtration can absorb that medicine so the water is purified again.

Overall, I don’t 100% like chemical filtration. I think it’s something you don’t need unless you get to that serious place that you really do need it to get the water clean. That sounds a little hypocritical, but there are a lot of steps you can take that don’t involve the chemical filtration and your tank will be better for it.

What Happens If You Don’t Filtrate Correctly

Filtration isn’t an easy concept, especially if you are new to it or haven’t owned a tank yourself before. However, hopefully you have a better understanding of how it works and what type of filtration you might be looking for.

Now, for the not so fun side. The issues that can arise if you don’t do it right. Keep in mind, if you follow instructions given to you with your fish, your tank, and any equipment you buy, you will be okay. However, if you get a little too lackadaisy you could run into some trouble.


This is a big one. We talked about how important it is that you have the correct biological filter in your tank, but why? If you have high levels of ammonia or bad bacteria, your fish just aren’t going to make it.

The most common time this happens is when you first start your tank. That’s because you haven’t oxygenated the water enough or provided some time for bacteria to accumulate. If you just put straight tap water in a tank and cross your fingers, your chances for fish survival are not great.

Another issue is not cleaning your tank properly. If you just let it go and don’t do anything, it’s going to get full of ammonia and nitrites. Your fish need fresh oxygen and a clean tank to prosper and have a good ecosystem. A build up of algae is not only unsightly but will put your bacteria out of balance and your fish will suffer.


If you mess up chemical filtration, the result can be dire. It’s one of the reasons I do not recommend using it. Messing with the biological filtration of your tank with chemicals is often not well thought out or researched. Mistakes are made quite frequently. I would hate to see you loose any fish because you decided to throw in an activated charcoal feature for the hell of it.

On the same hand, I’d rather see you use an activated charcoal filter than any other chemicals you could place in your tank. Be leery of anything you add to your tank! Your fish will thank you.


A mechanical filter is a pretty typical sight in any fish tank. However, if not taken care of properly, you are going to run into some serious issues. It’s important to stay on top of maintenance with your filter so you don’t lose any fish.

If you are relying on your mechanical filter to aerate, make sure you have the right size filter for the right size tank. If you don’t, you are going to have less than enough oxygen in your tank, you aren’t going to decompose bad bacteria. This can lead to a buildup of ammonia and nitrites.

Another issue that I see come up with fish tank filters is not taking good care of them. If you don’t do proper maintenance on your filter, you are almost better off without one. Filters need to be changed, charcoal needs to be replaced, and general cleaning needs to be done.

When you fail to do any of the above, you are making your filter work at less than an optimal level. If you filter isn’t working 100% your bad bacteria will creep up on you, your fish will get sluggish, and your oxygen levels will be sub-par.

What is the right fish tank filter system for me?

There is a lot that goes into putting your tank together. We’ve covered most of them already but let’s review the key points.


Make sure you have the right medium (think rocks, gravel, sand), proper oxygenation (aerator, mechanical filter), and keep your tank clean.


Buy the proper size for your amount of fish and size of tank, read up on how much aeration it provides, clean filters regularly, and follow manufacturer’s instructions to a ‘T’.


While not necessary in any tank, make sure you read instructions carefully, don’t over use, and take out after the need has been met.

Overall, you kind find a lot of different fish tank filtering systems that are going to work for your tank. Getting to know more about your fish and what kind of environment they will thrive in is a great starting point. From there, keep in mind your tank size and that good bacteria/oxygen balance.


All this talk of ammonia and nitrites has surely sunk in now, right? While not the most thrilling topic, fish tank filtration is something you need to know in and out if you want your fish to live a happy life.

Knowing the biological, chemical, and mechanical filtration systems and what you need for your tank is the difference between a healthy active tank and a sluggish and dirty tank.

Follow through with the three filtration systems and your underwater ecosystem will thrive. Your fish will thank you by staying active, healthy, and living long lives. There’s no reason you should have it any other way.

For more information on keeping your fish tank clean look at our article here.

4 thoughts on “Fish Tank Filtration and You: A Foundation to Your Healthy Tank”

  1. I would have never guessed that you needed bacteria in your fish tank. I had heard that ammonia is bad, but I never knew there was bacteria that could convert it to nitrate! I think I still have a lot to learn it seems.


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