top of page



Filtration has a few purposes in your aquarium. First of all it develops nitrifying bacteria that breaks down harmful compounds like ammonia and nitrites from your water, protecting your livestock. Secondly, it works as a sieve or strainer removing particulate matter from your water keeping your water crystal clear. It also allows for a place to run chemical media if needed. Sometime the only way to control or remove something is through chemical media, like ammonia or phosphate removers, carbon to remove tannis and medication, etc. Lastly, it provides circulation to your tanks water pushing clean, nutrients and Co2 enriched water throughout the tank. 


Filtration is pretty simple. We are going to start off by suggestion you get a canister filter as there are canisters sizes for all setups. They are just far more effective than most hang on back filters, and/or sponges. Ultimety, water gets sucked up into your filter, passes through 3 methods of filtration which are mechanical, biological and chemical and then get returned to your tank. Sponge filters do a good job at biological filtration, but are poor at mechanical filtration, and if you clean them too well you can kill all your beneficial bacteria. With most hang on back filters, they do not come with mechanical or biological filtration. They come with chemical filtration which isn't needed all the time. Out of the box, most hang on back filters are incomplete, and if you add mechanical filtration, most of the time the water will run over the biomedia instead of through it. They are just another ineffective method of filtration. This is why we suggest canisters.


When running a canister filter, we need to these trays need to be stacked in a specific order. With Fluval’s canisters, the water flows down to the bottom of the canister and makes its way up through the trays and out the top. But You need to check the manual of your canister filter to make sure you’ve stacked the trays in the proper order. The water should run through the stages in this order:

  1. Mechanical

  2. Biological

  3. Chemical (as needed)


Let talk more about the stages of filtration that a canister provides.


Mechanical filtration is the first stage of filtration which removes particulate matter form your water column. The idea is that the water should pass through smaller and smaller sponges until all the of particulate matter has been removed and your water is crystal clear. Now the sponges will also help with biological filtration, but we don't want to rely on them for that as we need to rinse out our mechanical filtration form time to time and we don't want to kill off our beneficial bacteria. If we keep our beneficial bacteria housed in our biomedia, we can beat up the sponges with heavy cleanings and not worry about crashing our cycle. We suggest you get course to medium to fine sponges setup in your canister. Most fluval canisters come with these sponges already, and if you have a little more room, we highly suggest running some filter floss as that get the water SUPER clear. 

Try running some filter floss in your canister to polish your water clean. You can buy it in large rolls which can last years depending on the size of your aquarium. The nice thing is that its cheap, so if it gets too clogged, you can throw it out and just add more. 



Biological filtration if the house in which your beneficial bacteria is going to live. In this area of the canister, it will converts any ammonia or nitrites into nitrates protecting livestock from harmful and potentially deadly compounds. Now you don't have to use anything fancy. We have been using ceramic rings for decades now and they work fine. We generally get a couple bags of them from our local fish store, but you can always buy them new online. There are also fancier biomedias like Seachem Matrix, but they really aren't needed unless you plant to have a LOT of fish in your aquarium, which we don't recommend with planted tanks as you'll constantly run into algae issues. Pretty much 99.9% of the time your filter is running, all you'll need is some sponges and you can fill the rest of your canister with biomedia. Its only every once in a while that you'll need chemical filtration which we'll talk about next. 


Chemical filtration is a type of filtration that should be used to address a larger issue. To use them seem more like a bandaid than a solution. The only exception where we'd use chemical filtration is with carbon. But let's go through all the different types of chemical filtration and how to use them. 


Carbon is used to remove tannis, chemicals like fish medications, but will remove some macro and micro nutrients from the water column so we don't want to run it all the time. Carbon is the only thing that ASG would suggest running as needed. 

Granulated ferric oxide or GFO (Phosphate remover)

GFO is used to phosphates from the water. High phosphates can cause algaes like black beard algae and filamentous algae. GFOs can be great a removing phosphates from the water, but we should really be using an RODI unit at this point to scrub the water of excess organics prior to putting it in our tank. Even with running GFO we can still phosphate based algaes just because the GFO doesn't remove organics immediately. 

Ammonia Removes

Pretty self explanatory, these remove ammonia from the water. High ammonia is obviously dangerous to your livestock, but can also cause algaes like staghorn. Most of the time hobbyists will use this chemical filtration when they have ammonia or ammonium in their tap water, and they are trying to suppress it in their aquarium. but again, at this point we should really be using an RODI unit to scrub the water clean before putting it into our tank. It might be nice for a short fix, but I would not rely on it full time. 

Peat granules

Lastly we have peat granules, or peat moss. Some suggest to add this into your filter to help soften your water through the release of tannis. But similarly to calcium carbonate, we don't suggest you toss anything into your tank that you don't have full control over. If you need to soften you water, we suggest you do with RODI water, not with chemical filtration.


Our final thoughts about chemical filtration are... if you have to run chemical filtration for any reason, there is a good chance that you are trying to fix a long term issue with a short term fix. Chemical filtration can be great for little fixes, but we'd suggest you look at the larger issue and try to fix the root cause.  


And the answer is quite simple as it relates to turn over. No matter what filter you decide to go with or have access to, it is wise to have enough filtration to turn the entire aquariums water volume over, 10x in one hour. Depending on the size of your tank, that might mean that you need to run two filters. Just know that the gallons per hour rating, or GPH, of the filter is generally taken by the manufacture with no sponges or biomedia in the filter at all. The manufactures simply run the filter empty and take a turn over reading. So, when you load up your filter with sponges and or biomedia, the turnover is going to decrease a bit. Just something to keep in mind when shopping for filters.


Also, its better to have a too much turnover, than too little. Another reason why we want to shoot for 10x turn over an hour, is for circulation reasons. When dosing the EI method and injecting Co2, its important to have all the nutrient rich water around the tank. We want to make sure there are no dead spots in the tank where plants wouldn’t have access to this nutrients, Co2 or fresh water. We at the ASG recommend a going with a canister filter due to:

1) They can easily achieve 10x turn over per hour

2) They can be customized easily to our tanks needs.


Now, we know we are going to get some hate for this one, but we DO NOT suggest going with sponge filters, and we are kind of on the fence about hang on the back filters, or HOBs. They are not bad options for other applications, but just not for planted tanks. So, lets talk about sponge filters a bit more. 

Fluval Canister.png


Now, every 4-6 months we need to crack open the canister and service it. This just entails rinsing and ringing out our sponges, or replacing them if they are looking sad. We should also rinse off the gunk from our biomedia if there is any, and we use a tooth brush on the impeller and housing to make sure no algae is building up that would restrict the flow of the pump. However, when servicing the canister, we need to tank water and NOT tap water. The chlorine in the tap water can kill your beneficial bacteria, crashing your cycle. If you do end up crashing your cycle, we designed a flyer that can help you navigate that situation, which you can find here. We like to siphon some tank water into a 5gal bucket when processing a water change and use that to dip and rinse everything out. Again, the biomedia houses the beneficial bacteria which develops when cycling your tank. This bacteria is responsible for breaking down the ammonia and nitrites, that your fish constantly produce, into nitrates, which is a less harmful compound for your livestock. So again, just make sure you never rinse anything from your filter in non-dechlorinated tap water. And one last note, you can never OVER filter your aquarium, but you can definitely under filter, hence why we think, the more biomeida, or ceramic rings, or whatever you are using, the better.


First, they are not going to achieve the 10x turn over per hour that we are looking for. This leaves more toxic organic compounds floating around with your fish. This lack of turnover also prevents the sponge filter from polishing the water and removing free floating particulates… which again, is their only JOB! Most sponge filters on the market come with a course sponges attached to them, which is better for flow, but then allows for smaller particulate matter to pass right through them, only catching larger organic material like dead plant leaves or bigger amounts of detritus. You can buy a finer sponge to swap out the courser one that comes stock, but then gets all gunked up, restricts the flow, reducing its turnover and effectiveness. Furthermore, there is almost NO customizability to your tanks needs with sponge filters. Like, what if you had a need to run carbon?... couldn’t do that with sponge filter. Or what if you wanted to run filter floss to polish the water super clear?! Couldn’t do that either. And unfortunately, we see this all the time with those starting out in the hobby, the hobbits rinses out the spouge with tap water, crashing their cycle!… It’s an honest mistake, but can be lethal to the tank and its inhabitants. We’ve also seen hobbyists bumping the sponge while performing maintenance and it expels everything is been holding onto for the week into the tank again… which again, defeats the purpose. That and you have all this rotting organic material that the sponge has collected, sitting in your tank with your fish. We just don’t get it. And lastly, which is more of an opinion, we just think they are super ugly in a tank. I mean, come one, we work really hard to make our tanks to look super beautiful, and then toss a massive black sponge hanging out in our tank… it just seems counterproductive… but again, we know this last part is more of our opinion… to each their own. So then, what about HOBs, or hang on back filters.

Sponge Filter .png


From our perspective, hang on backs can be an ok method of filtration so long as the hang on back functions like a canister. Hang on backs are generally a better option than a sponge filter but they still lack the filtration power and customizability that we appreciate from a canister. If you are going to use a hang on back filter, make sure it has a dedicated area for mechanical, biological and chemical filtration which the tanks water can flow through, and not just over. Hang on backs will have a higher turnover of water volume over a sponge filters, depending on which one you buy. If all you had access to is either a sponge filter or a hang on back filter so long as you have dedicated mechanical, biological and chemical filtration. We've seen many canister like hang on back filters online from random brands, but if you want a main stream brand, check out Fluval's C2, C3, and C4 lineup. They function like canister that hang on your class. Overall, if you have the room for a canister, we suggest you go that route. If space is limited, then we'd suggest a hang on back over a sponge filter. Links to these products are down below.

Recommended Products

Canister Filters

Fluval 107.jpg
Fluval FX2.jpg
Fluval 207.jpg
Fluval FX4.jpg
Fluval 307.jpg
Fluval FX6.jpg
Fluval 407.jpg
Zoomed Canister.jpg

Hang On Back Filters

Fluval C2.jpg
Fluval C3.jpg
Fluval C4.jpg

Mechanical Filtration

Fluval Bio Foam.jpg
Filter Floss.jpg

Biological Filtration

Fluval Bio Rings.jpg
Seachem Matrix.jpg

Chemical Filtration

Fluval Carbon.jpg
Fluval Phosphate Remover.jpg
Fluval Ammonia Remover.jpg
bottom of page