A different look at filtration | The best methods for aquarium filters
There are countless articles and videos on how to properly set up filters for your tank and what to look for, so I won’t recreate those. What I will do in this article, however, is explain what I’ve learned from setting up 40+ low and high tech tanks. All my tanks have different stocking, different sizes, different needs, and different requirements, naturally meaning they’ll all need different methods for filtration to keep things running smoothly.
To start, though, we need to quickly cover the nitrogen cycle. If you already know the nitrogen cycle, I still recommend skimming as I cover a few things that many aquarists might not know.
The Nitrogen Cycle
The nitrogen cycle is an overarching term meaning, basically, “The scientific explanation of how things underwater don’t die”. You can find a million explanations of this in more depth, but I’ll cover what I personally think is extremely important, and I’ll also explain what the pre-cycled biomedia we sell does.
If you’ve lived on this planet for more than about 5 years you probably know that anything wet generally decays way faster. When stuff decays in water, it releases ammonia (NH3). Ammonia is bad. It’s toxic, smells like ass, and kills your fish.
Luckily, there are bacteria that actually feed on ammonia- thousands of different species of them. These bacteria are called aerobic bacteria because they consume oxygen and ammonia, which is perfect for our fish tanks! But remember that bacteria are incredibly small, so you’ll need millions of these bacteria for them to make any considerable impact on the ammonia in the water. Fortunately bacteria multiply very quickly, so you’ll get to that number very quickly.
But wait, that’s not it. Because these aerobic bacteria do consume ammonia, but they don’t just turn it to nothing. They turn it into Nitrite, which is still toxic to your fish. In about the same amount.
This is why when you test your aquarium water, you always want to test for ammonia AND nitrite. Both are toxic, and just because you have 0 ammonia doesn’t mean you have 0 nitrite.
But, luckily again, these aerobic bacteria also consume nitrite, and convert it to nitrate, which isn’t toxic to your fish (at least not unless it’s extremely high concentration). I easily remember this because an “A” is a good grade, so nitrAte is good. Nitrates can simply be removed from your water with water changes or consumed by plants, as nitrate is the primary nutrient plants consume.
The idea is to set up your filter so that you can have as much aerobic bacteria living in it as possible, and the bacteria will also make a home on all the surfaces in your tank and in the gravel, but they don’t live in the water itself, just on surfaces. This is called “cycling” - and once you have enough bacteria that they can properly convert all of the ammonia generated by your tank from waste into nitrate, your tank is cycled and fully safe for stocking.
But that’s still not all, and many aquarists think that’s everything.
There’s a whole different type of bacteria called anaerobic bacteria. If aerobic bacteria thrive in oxygen-rich environments, anaerobic bacteria thrive where there is no oxygen. Namely, this means they thrive deep in your substrate, or deep in the crevices of biomedia in your filter (which is why it’s important to use stone biomedia rather than ceramic!)
Anaerobic bacteria do still help with your cycle and still help break down ammonia. More importantly, however, they actually help break down nitrate into nitrogen gas. This is the final step of a cycle.
Why does this matter?
You may notice that after setting up any new tank, after the cycle is fully complete and there is zero ammonia or nitrite in your tank, your aquariums will almost always become overrun with algae for about a month or so. I call this the “Algae cycle” which is the true final step of a cycle before your tank is “mature.” This algae cycle happens because your tank doesn’t have enough anaerobic bacteria yet, so all the nitrates not being consumed by plants are being used to grow algae.
You can build your tank with deeper substrate, especially by using lava rock or biomedia underneath your finer substrate, to promote anaerobic bacterial growth and to ensure less algae and better plant growth.
How to pick a filter for your tank
Different tanks need different filters. In general, all your filters need to check these boxes:
Mechanical Filtration - A fine sponge or pad is the very best option, but anything that’ll grab fish poop out of the water
Biological Filtration - A coarse sponge works fine, but space for lots of biomedia is better
Flow - A good filter should create flow around the tank. You don’t want your water stagnant.
Aeration - Your filter should churn water, either with bubbles or by agitating the surface of the water.
I’ll keep it short and explain the different filters I personally use, and link them in this article.
Breeding Tanks (Guppies, Shrimp)
In my breeding tanks, I use an electric sponge filter. I prefer the electric pump over air pump purely because I don’t want to run airlines to every single tank when I already have CO2 run to every tank in my fish room, but bubble operated sponge filters work great too. Either way, the main point with these filters is that they’re not only sponge filters, they also have biomedia and they create flow. And, most importantly, there’s no risk of sucking up fry and shrimp have some biofilm to feast on on the sponge.
High Tech Planted Tanks
(Or just any tank, really)
In most of my tanks with CO2 injection that aren’t breeding small creatures, I use this SunSun brand filter. It’s awesome.
It has a UV light, a surface skimmer, and has the best layout of media I’ve ever seen. It’s an easy to remove basket that’s tiered with a coarse sponge on the bottom, a box in the middle for chemical filtration or extra biomedia, and a big box of biomedia on top. It’s silent, creates great flow, keeps the surface clear of duckweed and protein film, and the UV clarifier keeps the water from turning green.
Big Tanks (40g+)
In my larger tanks, I use a canister filter like this one. The “SunSun” brand is perfect for this, also known as Polar Sun on Amazon. It’s a lot easier to clean and lasts a lot longer between cleaning. I especially like the ones with UV light built in, which prevent green water and help reduce algae.
Canister filters work best and look best with stainless steel lily pipes with a surface skimmer.
https://amzn.to/3UJudqi
