Thinking about adding aquarium sump tanks to your display?
This article will help you better understand what aquarium sump tanks are, why you may want one, and where to buy them online—with handy product reviews of the best setups.
Table of Contents
Already have a hang on what aquarium sump tanks are and how they function? Perfect, you can duck down to the product reviews with these handy links. But if you’re still getting your feet wet with saltwater tanks, you probably want to read through the entire article.
What Are Aquarium Sump Tanks?
Aquarium sump tanks are vital pieces of equipment that sit underneath your display tank. They contain everything, including your filter, heater, protein skimmer, and other equipment. If you buy a commercially made kit, you’ll probably get something that looks something like this:
Why keep all of your equipment within an aquarium sump tank? Well, other than convenience, obviously. But there are plenty of key reasons:
- When kept in or on your display tank, your equipment can turn into an eyesore. Keeping it below the tank (and under your stand) keeps it out of the way and out of sight.
- Keeping the equipment in the aquarium sump tank also provides you with easy access WITHOUT disturbing the living creatures in your aquarium. Then you can perform maintenance or replace anything at any time.
- An aquarium sump tank also allows you to expand the water volume of your system. This provides your tank with more stability and the capacity to support even more saltwater fish, corals, and other invertebrates without the need for the larger footprint of a larger tank.
To give you a personal example, my current display tank is a 92-gallon (348L) corner aquarium. And my sump tank holds about 16 gallons (60.5L) of water. So my total system volume is around 108 gallons (409L) of water. That’s a SIGNIFICANT increase. And if you want to expand from 55 gallons (208L) to 71 gallons (269L)? All you need is an aquarium sump tank to pull it off.
Why does increased water volume matter? The larger your total water volume, the more stable your aquarium becomes. That’s because sudden changes—like a spike in salinity, a temperature swing, or an accidental overdose of additives—are diluted across a greater volume of water. For example, if a heater malfunctions or you accidentally add too much supplement, the impact on water parameters is less severe in a system with a sump than in a smaller, standalone tank. Sumps also help buffer against temperature fluctuations, as the extra water takes longer to heat up or cool down. Similarly, if a fish dies or a contaminant enters the system, the concentration of toxins rises more slowly, giving you more time to react.
However, there are trade-offs: more water means more to heat or cool, and you’ll experience greater evaporation, which requires more frequent top-offs. Still, the stability and safety margin provided by a sump are major reasons why they’re standard in most reef tanks.
Aquarium Sump Tank Design
Aquarium sump tank designs follow the same basic patterns, regardless of whether you create your own (more on that in a minute) or purchase a pre-made kit. The design allows for filtration and purification, ensuring your display tank’s water remains healthy and fresh:
- Water flows from the display tank down to the aquarium sump
- The water flows through a filter sock, which removes large particles and debris
- Water then enters the chamber holding the protein skimmer, where it’s skimmed using foam fractionation to remove organics
- Space permitting, the water next enters the refugium area, where water receives biological purification
- Water then passes through baffles to trap microbubbles
- A return pump then pushes the water up to the display tank
Sounds complicated, right? Don’t worry; we’ll break down each of the steps (and the individual pieces) next to give you a better idea of what’s happening in your aquarium sump tank.
While sumps add many benefits, they also introduce potential failure points if not designed carefully. Common issues include:
- Sump overflow during power outage: When the return pump stops, water from the display tank’s overflow and plumbing drains into the sump. If the sump isn’t sized to handle this extra water, it can overflow onto your floor.
- Return pump failure: If the return pump fails, water circulation stops, and your display tank may run dry below the overflow, risking pump burnout or livestock stress.
- Clogged filter sock or drain: If mechanical filtration becomes clogged, water may back up, potentially causing overflow or reduced filtration.
- Siphon breaks and backflow: If your return plumbing doesn’t have a siphon break or check valve, water can siphon back from the display tank into the sump during a power outage.
Design safeguards:
- Size your sump to hold all water that will drain from the display tank and plumbing when the pump is off. Test this by turning off your return pump and watching the water level.
- Keep baffle heights and sump water levels below the rim to allow for extra volume in emergencies.
- Install anti-siphon holes or check valves in return lines to prevent backflow.
- Regularly maintain filter socks and plumbing to prevent clogs.
- Consider an emergency overflow or high-water alarm for added protection.
By anticipating these risks and testing your system, you can prevent most sump-related disasters.
Filter Sock: Keeps Sump Tank Water Clean
A filter sock is typically the first filtration step in a sump, catching and removing large particles floating around in the water. Water flows through the sock, and any suspended particles are trapped, preventing debris from reaching the rest of your filtration equipment. This is similar to the mechanical filtration you may be familiar with in freshwater tanks.
Filter socks are made from fabric or mesh material, folded into a tube shape, and cover the pipes where water drains into the sump from the display tank. They act as a “sieve,” preventing anything big and bulky from getting through.
Maintenance matters: Filter socks get dirty quickly and need to be changed or cleaned regularly—often every few days in a well-stocked reef tank. If neglected, they can clog, causing water to back up or overflow, and can become a source of nitrate buildup as trapped debris decomposes. For this reason, some aquarists prefer alternatives like roller mats (automatic mechanical filters that advance dirty material) or filter cups (which hold disposable filter media). Roller mats reduce maintenance but add cost and complexity, while filter cups are easier to clean but may not trap fine particles as effectively. Choose the option that best fits your maintenance routine and tank needs.
Protein Skimmer
While filter socks are handy for catching the worst debris that comes through the aquarium sump tank, most reef aquarium hobbyists also install a protein skimmer in the aquarium sump tank. And that’s because a protein skimmer isn’t officially a filter. But it DOES provide water purification.
A protein skimmer is a device that cleans your reef aquarium water using nothing but physics and bubbles (or is it bubbles and physics?). Tiny scrubbing bubbles remove all kinds of nasty stuff from your aquarium. (No, not the kind of scrubbing bubbles you use when it’s time to tackle the bathroom on cleaning day—though the principle is kind of the same)
Technically, you can install the protein skimmer anywhere you want within the sump tank. I prefer to put the protein skimmer upstream of the refugium. Putting the protein skimmer AFTER the refugium means losing skimming off all of the beneficial invertebrates your refugium is producing. (Which means you spent money on an additional component for your aquarium sump tank that isn’t helping you out)
Skimmer placement and tuning: Protein skimmers work best when the water level in their chamber is stable and within the manufacturer’s recommended range. If the water level fluctuates, skimmer performance can drop, or the skimmer may overflow. Oversizing a skimmer can lead to inconsistent performance, while an undersized skimmer may not keep up with your system’s needs. Contrary to popular belief, “bigger is not always better”—choose a skimmer rated for your system volume and bioload. Regular tuning and cleaning are also important to maintain efficiency and prevent noise or overflow issues.
Refugium in a Sump Tank
Aquarium sump tanks with a refugium are a naturalized part of the setup. Here, impurities are removed from the water naturally by the organisms living in the refugium. (In other words, you have your own colony of living purifiers—which is pretty cool when you think about it)
Many aquarium owners will use the aquarium sump tank refugium when they have deep sand beds.
Deep sand beds are live sand that serves as the home to aerobic (oxygen-loving) and anaerobic (non-oxygen-loving) bacteria. These bacteria act as the waste-processing plants inside your aquarium sump tank and turn ammonia into nitrites, nitrites into nitrates, and then completely remove the nitrates from the system. This prevents unwanted wastes from accumulating in your tank. That means a healthy environment for your marine tank—not to mention a natural cycling system.
In addition to deep sand beds, a typical sump refugium will also have macroalgae (like Cheatomorpha) and other tiny invertebrates. They perform the same handy “sterilization” technique.
It’s also popular to add live rock to the aquarium sump tank refugium to provide additional biological filtration capacity—while providing a substrate for your invertebrates and bacteria to grow on.
Because the sump remains below your display tank (and, thus, away from the predators you keep in your tank), tiny beneficial invertebrates called copepods often live and reproduce there. So if you’re looking to form a beneficial and natural live food for your fishes and corals? A refugium is the best place to do so.
Refugium operational tips: The effectiveness of a refugium depends on several factors. Lighting is crucial—many hobbyists run refugium lights on a reverse photoperiod (opposite the display tank) to help stabilize pH. Flow rate should be moderate: too fast, and organisms can’t process nutrients; too slow, and detritus can accumulate. Regularly harvest macroalgae to export nutrients, and monitor for pests (such as unwanted algae or hitchhiking invertebrates) that could spread to your display tank. The size of your refugium relative to your total system volume also affects how much nutrient export you can achieve—a larger refugium generally provides more benefit.
Baffles
Now we come to the baffles part of the aquarium sump tank. Baffles are narrow walls that force the flow of water over and under the walls, sequentially, to trap the bubbles created by water flow AND the filtration and sterilization processes of the other components. All of the twists and turns serve to remove the bubbles from the water:
- Bubbles are forced (depending on your setup; it may be a passive process) under the first baffle due to water flow.
- The bubbles remain trapped at the top of the second baffle. Remember, bubbles float.
- Bubble-free water then flows out under the last baffle.
Not all sumps have the same number of baffles, but you can see a general concept in the image above. You don’t want to force TOO many bubbles back out into your tank. They’ll obscure the view on your display tank, for one.
But they can also help modulate the flow of water returning to the tank. If you end up with an obstruction at any point in your aquarium sump tank? (Say, because you forgot to change out those socks) The baffles will prevent a sudden flood of water from rushing back to your tank. You DON’T want that to happen and lead to a flood. So while “bubble control” sounds silly, baffles are also important design features for water flow control.
Baffle design trade-offs: The spacing, height, and number of baffles affect how well they trap bubbles, reduce noise, and maximize usable sump volume. Baffles placed too close together can restrict flow and trap debris, while baffles that are too high reduce the sump’s available “emergency” volume for overflow events. Too few or poorly positioned baffles can allow microbubbles to reach the return pump, sending them into your display tank. When designing or choosing a sump, look for well-spaced, appropriately sized baffles to balance bubble removal, noise reduction, and maximum water capacity.
Return Pump
A return pump then sends the water up to the aquarium. After all, you’re working AGAINST gravity. Without the assistance of a return pump, the water can’t get out of the aquarium sump tank. Instead, you’ll end up with a pressure problem, which WILL result in a leak all over your floor, eventually.
Choosing and safeguarding your return pump: Select a return pump that can deliver your desired flow rate at the “head height” (vertical distance) between your sump and display tank. Manufacturers usually provide flow curves to help you match pump performance to your setup. Too little flow, and your filtration won’t be effective; too much, and you may create noise or overflow issues. Plan for pump failure by installing check valves or anti-siphon holes in your return plumbing to prevent backflow and flooding during power outages or pump shutdowns. Regular maintenance and periodic testing of these safeguards are essential for long-term reliability.
DIY Aquarium Sump Tanks
Since the commercially available aquarium sump tank options tend toward the pricey side, many people chose to build DIY aquarium sump tanks. This can be as simple as a 10- or 20-gallon (10-78L) aquarium where water collects and gets recirculated, or you can go as sophisticated as some of the more popular commercial models. You can even add filter socks, baffles, a refugium, and even automatic top-off (ATO) devices.
The advantages of building a DIY aquarium sump tank are cost savings and the ultimate ability to customize the tank with whatever you might need. The downside is that you have to design it and do all the work yourself. (Depending on your aquarium geekiness? That may NOT be a downside!)
DIY or Commercial? A Decision Framework: DIY sumps are a good fit if you have a nonstandard stand, need specific features, are comfortable troubleshooting leaks or plumbing, or want to save money. Commercial sumps are safer for those who want plug-and-play reliability, warranty support, or are less comfortable with custom fabrication.
Common DIY pitfalls to avoid:
- Using non-aquarium-safe silicone or materials that can leach toxins
- Underestimating the required sump volume (especially for power outage drainage)
- Poor baffle placement leading to microbubbles or noise
- Improper overflow or return plumbing design
- Skipping leak tests before installation
Careful planning and research can help you avoid these mistakes and build a reliable, effective DIY sump.
Building your own DIY aquarium sump tanks are projects on their own. But this helpful YouTube video can get you started on the right path:
Product Reviews
Maybe the DIY route isn’t for you. Not a problem. You can generally find aquarium sump tanks for sale at local pet stores specializing in saltwater aquarium fish. You can also find great options online.
To help you out, I’ve provided product reviews for the most popular models available on Amazon:
ProClear Aquatic Reef Sump RS100
The ProClear Aquatic Ultra Reef Sump RS100 is rated for tanks 100 gallons (379L) or less.
Made in America, the aquarium sump tank’s dimensions are 24″ x 10″ x 16″. They use a standard 200-micron bag/filter sock, making replacements easy and inexpensive to maintain over the long haul. This design uses a bubble diffuser tube to remove bubbles. That means lower noise for you to cope with.
Aqueon 34500 ProFlex Sump
Another good option is the Aqueon 34500 ProFlex Sump. This aquarium sump tank is designed to be flexible enough for you to create the sump design of your choice.
Do you want an old-school wet/dry filter? Hopefully not for a reef tank, but maybe you want to use this with a FOWLR or freshwater tank after you’re done. No problem—it’s that versatile.
Want to have a refugium? It’ll handle that addition.
Need to adjust the water height for your protein skimmer? It lets you manage such things without a problem.
The Aqueon ProFlex comes in a few different sizes, depending on the size of the tank you plan to attach it to:
- 55 gallons/208L with dimensions of 19 7/8 ” x 9 7/8″ x 17 1/4″: Model 1
- 75 gallons/284L with dimensions of 29 7/8″ x 9 /8″ x 18 7/8″: Model 2
- 110 gallons/416L with dimensions of 25 7/8″ x 13 3/4″ x 17″: Model 3
- 210 gallons/795L with dimensions of 36″ x 13 3/4″ x 18 7/8″: Model 4
If you go with this aquarium sump tank, make sure you watch out for some key problems. Several people who purchased this unit online reported the sump arrived with a crack in it, had broken parts, etc. You should inspect anything you purchase online. But since you will be plunking down a couple hundred dollars for an aquarium sump tank? You’ll want to carefully inspect everything when you receive them to make sure they are defect-free. There’s NOTHING worse than coming home one day to a soggy carpet because your sump leaked.
Another con is that owners reported the filter socks were challenging to remove. (No one likes that)
Eshopps AEO14005 Reef Sumps
The Eshopps AEO14005 RS-100 is designed for simplicity and affordability. Rated for a 75-100 gallon (284-379L) aquarium, it’s a great option if the space is limited in the stand under your display tank.
The dimensions of the Eshopps AEO14005 RS-100 (according to the manufacturer’s website) are 24″ x 12″ x 16″. The protein skimmer compartment is 9″ x 11.5″, fitted with a 7″ micron bag/filter sock. It also comes with a flexible hose that you can attach to your bulkhead or overflow and a pre-filter sponge that rests between the baffles to help provide biological filtration and dampen the noise of your aquarium sump tank.
It’s quiet, compact, and affordable. Something else to consider is aesthetics. Do you like an elegant, clean look/design?
On the other hand, though, if you have space for a larger aquarium sump tank, you should select a larger model that will allow for a refugium. If you have a tank larger than 100 gallons (379L) or have more space under your aquarium to fit a 30-inch or 36-inch long sump, consider getting the Eshopps 14010 RS-200 or Eshopps 14015 RS-300 models.
Keep in mind, though, Eshopps wants you to buy the proprietary filter sock. That’s challenging as you won’t be able to use a generic.
One thing I love about the Eshopps reef sump is how quiet it is. But don’t take my word for it. Watch this YouTube video with your volume turned up:
If you want to make sure it’ll fit in the space you’ve allocated for your aquarium sump tank, here are the ratings and dimensions for each of the models:
- 14005 RS-100: Aquarium 100 gallons (379L) or less. Dimensions of 24″ x 12″ x 16″
- 14010 RS-200: Aquarium 125-225 gallon (473-852L). Dimensions of 30″ x 12″ x 16″
- 14015 RS-300: Aquarium 225-300 gallon (825-1136L). Dimensions of 36″ x 14″ x 16″
Aquarium Sump Tank Comparison Chart
| Model | Max Tank Size | Refugium Option | Noise Level | Ease of Maintenance | Filter Sock Type | Price Range |
|---|---|---|---|---|---|---|
| ProClear Aquatic RS100 | 100 gal (379L) | Limited | Low (bubble diffuser) | Easy (standard sock) | Standard 200-micron | $$ |
| Aqueon ProFlex (various) | 55–210 gal (208–795L) | Flexible/Modular | Moderate | Challenging (sock removal) | Proprietary | $$$ |
| Eshopps RS-100/200/300 | 100–300 gal (379–1136L) | Yes (larger models) | Very Low (quiet design) | Easy (but proprietary sock) | Proprietary | $$ |
How to choose? Prioritize features based on your needs:
- Reef tanks: Look for sumps with refugium space and quiet operation.
- FOWLR or freshwater: Flexibility and modularity may be more important.
- Small stands: Compact models like the Eshopps RS-100 fit tight spaces.
- Low maintenance: Standard filter socks are easier to replace; roller mats (if available) reduce manual cleaning.
- Budget: Compare price versus features, and factor in the cost of proprietary replacement parts.
Best Aquarium Sump Tank Review
Looking for the best aquarium sump tank for your reef tank? I’m happy to supply a recommendation based on my personal experience.
Proclear is always an option, but there aren’t many reviews, which makes me a bit nervous.
I was initially attracted by the flexibility of the Aqueon ProFlex design. I liked the idea of standard accessories and ways to change things up. But there are minimum requirements (for me) when looking at an aquarium sump tank setup:
- It can’t leak
- Has to be easy to maintain
- Difficulty getting the filter socks out
Throw in the fact that many of these sumps are reported to have arrived cracked, and it leads me to skip that one.
For me, the best blend of attractiveness, simplicity of design, and functionality are the Eshopps Reef Sumps.
To get the best functionality, you’ll want to pick the largest model that will fit under your aquarium.
My Recommendation for Best Aquarium Sump Tank
For More Information
Hopefully, you found this information on aquarium sump tanks helpful. If you are looking to set up your reef tank with the best equipment and gear, you can continue the journey here:
What do you think? Would you like to add a recommendation for aquarium sump tanks you prefer? Please leave a comment below if you do.
Hi all, I’ve been a marine aquarium enthusiast for about a year, but only recently had a company in town setup a Bashea 30″ system, along with a powerful protein in sump skimmer and an eshopps evaporation filler. My primary media is my socks of course, carbon, but also a variety of seachem products I love, including denigrate, matrix,their phosphate remover, and their Purigen product. A fixed rate return pump finishes the setup.
I had to have an overflow box install, as my tank is not plumbed.
Challenges so far? Getting the in flow rate and out flow rates to always be in balance, and to protect from overflows by keeping the levels in both the main tsk and sump set properly. Still a bit tricky . I added a ball valve after the return pump a few days ago and with some tweaking, I think I’ve go it.
No space set aside for a refugium right now, but I think I could allocate space for it.
Questions to the pros ..
100, 200 or 300 micron socks? Felt or not. Some slow the flow like crazy and the felt ones are almost impossible to get clean but hold up well. Recommendations?
I’m new to the Bashea brand. Any thoughts on the quality ? I just trusted the vendor.
Finally, anyone feel my media choices are newbie crazy? Finally, should I switch to a D.C. adjustable pump? Is slowing the flow of a ac pump going a bad idea?
Thanks for the comment, David, and asking for feedback from the community. I’m curious to see what others say in response.
Correction …de nitrate product, not denigrate.