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Are Saltwater and Freshwater Filters the Same? (Learn What Filter You Should Use)

I know it can be confusing for a new aquarium hobbyist when it comes to filtration for marine or freshwater tanks. I have been in the hobby for over 30 years now and sometimes even I need to stop and think about different aspects of keeping a specific fish tank myself. So, I get it. In this article, I hope to clear your mind and set you straight on saltwater and freshwater filtration system. So, let us begin.

The filters you purchase for saltwater and freshwater tanks are the same. There are different aspects to consider when it comes to purchasing a new aquarium filter for these two types of tanks. These include water flow and whether (or not) mechanical or biological filtration is needed. 

There is more to this filter question than that quick answer. So, that is what we will discuss in this article – what a saltwater tank requires and what a freshwater tank requires for filtration. I have had a hang on back style filter on a saltwater filter for years with no problems.

I have also run a Fluval canister filter on a freshwater tank for years and everything ran smoothly. I used a Fluval 305, which I am not sure is made anymore. I checked out Amazon and I really like this Fluval 306. I would not hesitate to use it on a freshwater or saltwater tank.

You need to understand what filtration is best for the size of your tank and requirements of the aquarium’s inhabitants. It is not confusing, so you need not worry. I will explain everything you need to know in detail below so please keep reading…


What are the Differences Between a Saltwater and Freshwater Filter?

The biggest difference for filtration on these two types of tanks is the size of the filter you have. You will need much more water movement in most saltwater tanks than in a freshwater tank. Take a 55-gallon aquarium, for example. If you are running a freshwater 55-gallon tank, you could get away with a hang on back filter like this Aquaclear 70 model. I would also recommend adding a power head on the other end of the tank to maximize the water flow so the filter can more easily do its job.

For a saltwater 55gallon tank, this Fluval canister filter is a beauty. Make sure to place the inlet and outlet tubes at opposing sides of the tank and that should be good enough for water flow. A canister filter works fine for a freshwater tank, however, it works even better for a saltwater one, in my opinion, because they have way more space inside for multiple types of filter medium to suit your needs.

With this comparison, if you were to run these two tanks side by side you would be able to visibly see the higher rate of water flow in the saltwater tank using the canister filter. You might even think the salt tank has too much movement. It does not unless you are planning on having seahorses in the tank.

Both filters could potentially have the same filter medium in them and both successfully harboring bacteria and cleaning out the tank, whether your requirements are mechanical, biological, or chemical.

This then means the main difference between a saltwater filter and a freshwater filter is the amount of flow rate it puts out. This also means they are the same types of filters because you could use these filters for saltwater or freshwater aquariums interchangeably.  

Can You Have Too Much Filtration in a Saltwater Aquarium?

After all this talk about having more water flow in a marine tank well, it is a good question to ask. Can a saltwater tank be over filtered?

Honestly, I cannot really think of a reason how you could have too much filtration in a saltwater tank. Of course, if you are being ridiculous and you hook up something rated for a 300-gallon tank and put it on a 50-gallon version or smaller, then sure that is too much. Most people are not going to do that, however.

The only other time I can think of when a saltwater tank might be over filtered is if you have seahorses or other fish species that require a calmer tank. Most people will not have seahorse though, as they are very finicky creatures and hard to keep in captivity.

So, do not be cruel and buy seahorses if you have not been in the hobby for at least 10 years. I made the mistake a few years after being in the hobby and ended up with a dead seahorse after just a couple of weeks. I felt much worse about the fish dying than the money spent.


What is the Best Filter for a Saltwater Tank?

I know you are probably thinking I will automatically say a canister filter in answer to the question. You would be mostly right. I like canister filters because of the size of their filter medium area, which allows you to add quite a bit of materials to filter the way you want.

I also like canister filters because the tubes can be easily placed at either side of the tank. You can also add inline UV sterilizers and inline heaters to them quite easily maximizing the health of the tank, especially with the UV sterilizer.

I gave a couple of good options above for canister filters available from Amazon. Check them out.

Canister filters are not the end all or be all for saltwater tanks, however. I ran an Aqua-clear HOB filter on a 30-gallon tank for 5 or more years and it worked great. The tank had a minimal amount of fish in it and it always had clear clean healthy water. The tank was over 25 years old and I decided to get rid of it and transfer the fish.

So, you do not really need a special filter for a saltwater tank. You can use a canister for saltwater or a hang on back, if the tank is smaller. I would say smaller means under 60 gallons.

Most likely, you will also use a protein skimmer on a saltwater tank and that will help the filtration. A protein skimmer is not necessary for a freshwater tank.


What is the Best Filter for a Freshwater Tank?

Honestly, most filters will work fine for a freshwater tank. In this article, I have only talked about HOB and canister filters but there are other types, such as corner filters and powered internal filters. If you have goldfish in a good-sized tank, you could use a corner filter but for most tropical fish. I would recommend the HOB or canister type.

As far as which one is the best filter, well, we have discussed why you would use either. I guess if you want a lot more water movement, then get a canister filter. HOB filters are the more economical option and if you ended up wanting more water flow, you could always add a power head down the road.

For an HOB filter that I like I linked above to this Aqua-clear model and yes there’s another link. 

For canister filters, please scroll back up as I have offered some solid recommendations.


Final Thoughts

I want to remind you that any of the filters manufactured such as HOB or canister models are all good candidates to be used in either a saltwater or freshwater tank. What you should concern yourself with is how much water flow you will need, keeping in mind that a marine tank might need a higher rate of flow. So, you would select a canister tank.

Plus, I have not mentioned this yet but having a canister tank is nice when you have a set up where you can hide the filter out of the way. They are usually quiet anyways, but this just makes them even quieter. Canister filters also help to keep your tank free of pieces of aquarium equipment. After all, it is all about watching the fish (not the equipment) that attracted us to this hobby in the first place!

You can also use a canister on a freshwater tank. There is nothing wrong with having high flow in your tropical tank, unless of course you are housing a Betta fish. One last point about canister filters – they usually have quite a bit more room in their filter medium area than a HOB will have so this makes them that much more attractive to purchase.

It really sounds like I am favoring canister filters over HOB filters, but I am not. I have used HOB for years with great success and plan on continuing to do so. Just remember that saltwater and freshwater filters are essentially the same things.

I hope this article has been helpful to you. Thanks for reading and good luck with your tank.

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