Are Filter Socks Necessary For Reef Tanks? (Pros, Cons, & Alternatives)

Image Credit: Reef Tank Resource
Image Credit: Reef Tank Resource

Are Filter Socks Necessary For Reef Tanks? (Pros, Cons, & Alternatives)


Filter socks are inexpensive but time-consuming to clean – which is why some people choose not to use them. In this article, we will explore whether filter socks are necessary or if there are alternatives that may work just as well. We’ll also provide a helpful guide on how to easily clean your filter socks between uses.

What do filter socks do?

A filter sock is simply mechanical filtration. It can be a great way to filter out larger organic waste from the water column of your reef tank that may not get caught in the sump. It is also easy enough for most people with minimal reef tank experience or time on their hands – which is why they’re often recommended by hobbyists and experts alike.

Some of the benefits include how affordable a filter sock is, the ability to be reused, and the fact that a filter sock works well at catching debris and food that doesn’t get eaten as it sinks down into your tank’s water column where other methods might allow them to stay hidden in your rockwork or sump and breakdown before being removed by another means.

It’s best to remove larger organic debris before it breaks down into more harmful components such as phosphate, nitrate, ammonia, etc. A protein skimmer, clean-up crew, or healthy bacteria in your tank will eventually work to break down and remove larger detritus but it’s best to remove this waste early so these methods don’t get overwhelmed.

Do I need to use filter socks?

A filter sock is not necessary for a saltwater reef tank. A filter sock can be used to remove larger organic debris but there is no need if you have other methods of removing them such as protein skimmers, clean-up crew, or healthy bacteria in your tank. These other methods will eventually work on these particulates and break down the organics into less harmful components. The key is to ensure that you have a large enough clean-up crew, properly sized protein skimmer, and large enough bacteria population to handle the extra organics when there is no filter sock helping as mechanical filtration.

It’s better to not use filter socks if you won’t regularly clean them out. If not cleaned they’ll just become a source of harmful phosphates and nitrates that can cause algae blooms or cause fish and corals to become stressed or even die.

How do you use a filter sock?

The sock is placed inside the sump of your tank and water returning through the overflow to the sump will push through it. The filtered particulates are trapped in its fibers and can be removed with regular cleaning, which would cause clogging if not taken care of on regular basis (every few days).

Types of filter socks

DrawString vs Plastic Ring

DrawString filter socks

Drawstring style filter socks are essentially just drawstring bags made out of filter fabric material. The drawstring allows the sock to be fitted to the output of an overflow pipe.

Plastic ring filter socks

Filter socks with a plastic ring embedded in the opening of the sock are designed to be used in a sump with an opening that accepts the ring size and suspends the sock beneath the output of the overflow pipe.

Thin Mesh vs Thick Felt

Thin mesh filter socks

A thin mesh filter sock is a cheaper alternative to the thicker felt style. They are often used in conjunction with other filtering methods, such as protein skimmers or activated carbon filters because they do not remove waste from the water nearly as effectively – but instead, simply trap only the largest waste and allow for easier removal of this larger debris.

Thick felt filter socks

Thick felt filter socks are a more expensive but much better alternative to the thin mesh style. They trap many different sizes of particles and remove them from the water column, making it cleaner for fish in your tank.

Because they trap more particulates they need to be cleaned out more frequently than the thin mesh style socks.

4" Ring Filter Socks
200 Micron

200-micron filter socks will take longer to clog but will still remove larger organics.

7" Ring Filter Socks
200 Micron

200-micron filter socks will take longer to clog but will still remove larger organics.

4" Ring Filter Sock Holder
With Filter Sock

If you don’t have a filter sock section incorporated into your sump you can easily add one.

What is a micron filter sock?

Micron refers to the size of the particulates that the filter will catch and remove from the water column. A 100-micron filter sock will remove particles that are larger than 100 microns. A typical “micronic” particle is about 0,01 mm in diameter (or 100 μm). The smaller the micron designation of the filter sock the smaller the matter it will trap.

While a smaller micron filter sock will trap more organic matter and debris it also means it will clog more quickly and need to be cleaned more often.

100-micron filter socks are pretty common and as the first line of defense for mechanical filtration. Smaller micron socks will probably become clogged too quickly for most people.

Pros of filter socks


Filter socks can be a great way to save money on your saltwater reef tank. They are reusable and last up to 12 months or even years, which means you don’t have the constant need for new socks like with other methods of filtration in a sump system that might cost more over time than just purchasing a new filter sock or two.


Filter sock’s durability makes them perfect when it comes down to maintaining clean water quality while not breaking or wearing out quickly.


While they may already be inexpensive, filter socks can be cleaned and reused saving you more money. They need to be regularly rinsed and eventually, they will benefit from being thoroughly washed but they hold up very well and can be reused for years.

Can hold media

A sock can be a great place to run filter media such as Phosguard, Purigen, or even biological media such as MarinePure Balls. I should point out though that this isn’t a good location to put carbon media since the churning water will grind the soft carbon down to powder. A reactor would be a much better way to run filter media such as carbon.

Cons of filter socks

Can be time-consuming

Filter socks can get clogged quickly which means they frequently need to be rinsed out. Eventually, they will need to be thoroughly washed which can take more time depending on which approach you prefer for cleaning them effectively. Filter socks need more attention than other methods in a sump system that don’t require as much maintenance like a protein skimmer, refugium, or live rock for example.

Alternatives to filter socks

Protein Skimmers

A protein skimmer is a device that removes organic compounds from the water column. The bubbles created by this process attach to these particles and rise up, where they are collected in a “skim collection cup”. This type of filter has been used for decades as it’s one way you can keep your tank cleaner without using socks.


Refugiums are usually sections in your sump that you add a grow light and some macroalgae such as chaeto or sea lettuce. The macroalgae consume phosphates that may otherwise be food for unwanted algae in your main display tank.

While primarily home for growing macroalgae, refugiums are a great home for microorganisms such as copepods and amphipods. These tiny critters are an important part of a reef tank clean-up crew. They eat smaller organic debris such as uneaten food and fish waste.

Live rock

Every saltwater tank needs live rock for hosting beneficial bacteria. If you don’t want the hassle of filter socks you can add more rock to increase the area for beneficial bacteria to grow. This will allow your system to be able to handle breaking down more detritus than it would normally deal with when filter socks are used.

Clean-up crew

A good clean-up crew is a smart addition to any saltwater tank. Crabs, snails, and such will help break down larger organics more quickly so that they can more easily be removed by a protein skimmer or consumed by beneficial bacteria that will convert the detritus into less harmful components.

Roller Mat Filter

Several manufacturers have developed alternatives to filter socks typically called a roller mat filter. These filters work essentially the same as a filter sock but are designed to not need to be cleaned regularly.

It works by using a roll of fleece or filter fabric that the sump flows water through. When that section of filter fabric becomes clogged with debris the water level will begin to rise which triggers the roller to automatically advance and expose a new section of fleece or fabric.

This solution means you’ll only have to change out a filter fabric or fleece roll every couple of months. The downside is that they are not usually inexpensive, especially when compared with how cheap a couple of filter socks are.

How often should filter socks be cleaned?

Filter socks should be cleaned at least every 3 to 5 days under normal feeding conditions with a moderate amount of fish. As pieces of uneaten food, fish waste, and other larger detritus make their way down your tank’s overflow they will collect in your filter socks. The socks then get clogged and the organics will begin to decompose if not removed regularly. A sock that goes uncleaned for too long will also clog and no longer pass any which could cause water to back up and overflow into other parts of your sump.

The conditions unique to your tank may mean that you can get away with waiting longer between cleanings. Or you may find that you will need to clean them out more frequently. This mainly depends on how many fish you keep and how heavily you feed them.

If you’re unsure of how often is right for you to clean your filter socks you can stick to the 5-day method and you will likely be fine. You could also check them when you feed your livestock and if they look discolored it would probably be wise to go ahead and clean them. If you find that you are having trouble with algae, one course of action is to clean your socks more often.

Filter socks are designed to be washed in a washing machine, but can also just as easily cleaned with hot water. In the case of saltwater tanks where soaps are not recommended for use due to their high phosphate content, it’s important that you rinse them thoroughly before putting your tank back into service after cleaning! This will help prevent any unwanted algae blooms or other issues from occurring while maintaining healthy levels within our reef aquariums.

Some people choose instead to simply replace their used filter socks every few months instead of washing them. This is a reasonable approach since they’re fairly inexpensive. It saves the hassle of having to wash them and prevents the opportunity of introducing excess phosphates or chemicals from the cleaning process.

How long do filter socks last?

Filter socks can last anywhere from six months to a year, depending on the frequency of use and how often they’re cleaned. Although many people wash and reuse them for years without reporting any problems.

Filter socks are very inexpensive in the realm of reef keeping so replacing them on occasion shouldn’t be a budget buster if one tear or begins clogging more frequently.

User “scooter31707” from the Reef Central forum posts that he replaces his filter socks once they no longer come out white after two wash cycles. This sounds like solid advice for those trying to get the most out of their filter socks.

How to wash filter socks

Washing machine and bleach

In your washer with water (no detergent) and a couple of tablespoons of fragrance-free bleach, run a wash cycle with your filter socks. Put the sock in a mesh bag or pillowcase before placing it into the washer to help protect the sock from tearing and wear.

You may want to run a cycle with nothing in your washing machine except hot water to remove any detergents that may be left in it from the last wash cycle.

Bleach is not necessary, but it does help kill any bacteria that may have been growing inside of your sock.

Soak in a bucket with bleach

Soak the filter sock in a bucket of water with a few tablespoons of bleach for at least 30 minutes. Remove from soaking, rinse thoroughly with fresh tap water (no soap). Next, soak in a bucket of water with SeaChem Prime to neutralize the chlorine.

Spray with a hose or pressure washer

Probably the easiest method is to use a hose with a sprayer or a pressure washer. The force will blow the organics out of the sock material. Just spray the sock out until it becomes white again. A pressure washer will obviously be more effective but be careful with powerful gas-powered pressure washers. If you can, keep the pressure low until you get a feel for how much pressure will get the sock clean without damaging them.

SeaChem Prime

Ideal for neutralizing chlorine after using bleach to clean filter socks.

SeaChem Purigen

Removes organics from your water and can be placed in a filter sock.

SeaChem PhosGuard

Removes phosphates (that can cause algae) from your water and can be placed in a filter sock.

Filter socks for a reef tank - Yes or No?

Filter socks, in my humble opinion, are a “No”. The need to rinse them every 3 days or so is too inconvenient. Many of us get away with weekly maintenance and the idea of needing to attend to my aquarium several times a week just to run socks in my sump is more of a job than I’m willing to tackle.

They are a great option if you’re having problems with algae and high nitrates and want to see if filter socks could provide a quick fix, even if it’s only temporary.

You’ll need to make the call for your personal circumstances.

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