What's the Best Mechanical Filtration for a Reef Tank?
As reef keepers, we spend A LOT of money and time talking about things like lighting and flow, but there's one super simple area almost all of us could improve on: Mechanical Filtration.
What Is Mechanical Filtration in an Aquarium?
There are three main types of filtration we rely on in our aquariums:
- Mechanical Filtration: Physically trapping and removing uneaten fish food, fish waste, or any other floating particles from the water column. It's the most basic method of aquarium filtration and one that nearly every aquarium owner employs in one way or another.
- Chemical Filtration: Removes dissolved impurities from the water using media that absorbs unwanted substances. Common examples include carbon for removing discoloration and odors, GFO for lowering phosphate, and specialty resins for targeting specific contaminants.
- Biological Filtration: Relies on beneficial bacteria that live on rock, sand, and filter media. These bacteria convert toxic waste like ammonia and nitrite into less harmful nitrate. Biological filtration is the backbone of every stable aquarium.
Why Does Mechanical Filtration Matter?
Physically removing things from the water before they have a chance to break down is the most effective filtration method. It helps with maintaining stable nutrient levels like nitrates and phosphates and promotes clearer water overall.
To keep things simple, we are going to break mechanical filtration into three easy categories: Good, Better, and Best. This will help you choose the right option not just for your tank, but for your lifestyle and maintenance habits too.
Good: Filter Socks
Filter socks are the most common form of mechanical filtration in reef tanks. They come in a wide range of sizes with 4" wide being the most common. They work well, but only if you're willing to put the time into routinely changing and cleaning them.
Types of Filter Socks
Filter socks generally come in one of two styles: plastic ring or drawstring.
Felt Filter Sock with Plastic Ring
Felt Filter Sock with DrawstringPlastic Ring
Socks with a plastic ring are designed to sit in a dedicated filter sock holder in a sump, where water spills into the filter sock and passes through, leaving any floating particles trapped in the sock.
Drawstring
As the name suggests, drawstring filter socks have a drawstring instead of a plastic ring, making them ideal for sumps without dedicated filter sock holders. They can be attached to plumbing, catching any debris that would otherwise pass into the sump. Some can also double as media bags, making them a flexible option.
Filter Sock Materials:
In addition to the two different form factors, filter socks generally come in either felt or mesh material. Both have pros and cons, so it's important to decide what matters most to you before choosing which one to go with.
Felt Filter Socks:
Filter socks made from a felt material are the most popular filter sock option because they do the best job at trapping small particles and can be easily washed over and over again in a regular washing machine.
Mesh Filter Socks:
Mesh filter socks are great for basic mechanical filtration when you don't necessarily care about catching smaller particles. This means they last longer before overflowing. They can also be more easily cleaned by hand, but don't always stand up very well to being washed in a washing machine. Drawstring mesh filter socks are most common if you're using them to hold filter media.
Are Filter Socks the Best Choice For You?
| When You Should Use Filter Socks | When You Shouldn't Use Filter Socks |
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Tips for Using Filter Socks:
- Change them out twice a week for the most effectiveness, but once a week minimum.
- For felt socks, wash them in bulk to save time. Buy several socks and store them in a bucket with a tight-fitting lid to reduce odor. Turn them inside out and give them a quick pre-rinse before adding them to the bucket. Once you have several dirty socks, wash them in the washing machine with a bit of regular bleach. Run an extra rinse cycle.
Better: Filter Cups
Filter cups take the best parts of filter socks and make them more flexible. Filter cups are exactly what they sound like: a cup that sits in a filter sock holder where you can put filter pads, mesh media bags, or a combination of both, to help filter the water passing through.
Filter Cup Pros:
- Easy drop-in upgrade for most systems
- Can run mechanical and chemical media, even at the same time
- Swapping mechanical filtration pads or floss is quick
- Filter pads/floss are disposable, so no cleaning step required like filter socks
Filter Cup Cons:
- Still requires consistent manual maintenance
- Disposable filter pads aren't as eco-friendly
Are Filter Cups the Best Choice For You?
| When You Should Use Filter Cups | When You Shouldn't Use Filter Cups |
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Best: Automatic Fleece Roller Filters (Roller Mats)
Simply put, if you're looking for the most effective, hands-off mechanical filtration, automatic fleece roller filters are for you. They replace filter socks or filter cups entirely, eliminating the need for constant changes and cleaning. Fleece rollers are not just an upgrade. They completely change how mechanical filtration fits into your routine. In some cases, using an automatic fleece roller can even eliminate the need for a protein skimmer.
How Do Automatic Fleece Roller Filters Work?
These devices work continuously, in the background while you enjoy your tank. They have a roll of filter fleece and automatically advance based on a float switch, optical sensor, or timer to remove waste before it can break down into the water column. Once the roll is used up, you simply swap the dirty roll for a new one and the fleece roller gets back to work.
Fleece rollers are available for a wide range of system types, from systems with sump filtration to nano all-in-one style aquariums with filtration built into the rear of the aquarium. It's never been easier to run the best mechanical filtration!
Installing an AquaReady AF-1 Filter Roller
Red Sea NanoMat Filter RollerIs an Automatic Fleece Roller the Best Choice For You?
| When You Should Use an Auto Fleece Roller | When You Shouldn't Use an Auto Fleece Roller |
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Tip: You may notice reduced protein skimmer performance after installing an automatic fleece roller filter because less waste will reach the skimmer. If you don't already have a skimmer, but plan to add one, you may want to consider purchasing a slightly smaller skimmer than you'd typically use on a system without an automatic fleece roller filter.
Adam has been reef keeping since 2010 and got his start on the Bulk Reef Supply Customer Service team. He believes the best tanks are built around what you enjoy, not what’s trending. Adam is especially interested in simplifying the hobby, exploring the latest gear, and helping others focus on long-term success over chasing perfection.
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