The best reef sump is the one that fits your cabinet, holds every planned component and has enough empty capacity for drain-down when the return pump stops. Brand and display-tank ratings matter less than measured dimensions, operating water depth, plumbing layout and maintenance access.
This guide compares five current complete sumps and a DIY baffle-kit route. We did not add Amazon buying buttons because the exact current models could not be matched to trustworthy purchasable Amazon listings during our review. Manufacturer links are provided for current dimensions and configuration details.
Quick comparison
| Sump | Best suited to | Main consideration | Current information |
|---|---|---|---|
| Eshopps RS-100 5th Gen | Compact, conventional reef layout | Confirm current-generation dimensions and chamber fit | Manufacturer range |
| Trigger Systems Ruby30E | Flexible premium acrylic sump | Measure skimmer footprint and cabinet access | Manufacturer page |
| Fiji Cube Fiji-15 Advanced 2nd Gen | Compact system needing adjustable water depth | Select from the exact current size, not an old listing | Manufacturer range |
| IceCap 36 Reef Sump V2 | Larger equipment and an integrated refugium layout | Verify cabinet door opening and service clearance | Manufacturer page |
| Bashsea SS-30 | Heavy-duty build and adjustable chamber depth | Two-section layout may not suit every refugium plan | Manufacturer page |
| Fiji Cube DIY baffle kit | Customizing a compatible standard aquarium | Assembly quality and drain-down testing are the owner’s responsibility | Manufacturer range |
What a reef sump does
A sump is a separate water vessel, normally below the display aquarium, connected by an overflow and return pump. It increases total water volume, hides equipment, collects surface water for mechanical filtration and creates working space for a skimmer, heaters, probes, media, reactors or a refugium.
A sump is not automatically safer or cleaner than a well-designed sumpless aquarium. Incorrect plumbing, inadequate empty volume, blocked drains or an unprotected return outlet can cause flooding. The complete system must be tested with the return pump running and switched off.
Measure before choosing a sump
- Measure the cabinet interior. Record width, depth and height, then measure the actual door opening. A sump that fits inside the stand on paper may not pass through its doors or frame.
- Map the plumbing. Confirm the number and diameter of drain lines, bulkheads, emergency drain, return hose and unions. Never force incompatible pipe into a supplied fitting.
- Measure every component. Record the skimmer footprint at its widest point, recommended operating depth, return-pump dimensions, heater length and space needed to remove filter socks, cups or fleece rolls vertically.
- Calculate drain-down capacity. With the pump off, water drains from the overflow box, plumbing and display until the siphon breaks. The sump must hold this water without approaching the rim.
- Allow service space. Leave room to remove lids, clean chambers, change mechanical media and reach valves without dismantling the stand.
Features that matter most
Mechanical filtration
Filter socks, cups, floss trays and fleece rollers can all remove suspended solids. Socks and floss are inexpensive but require frequent cleaning or replacement. Roller compatibility may reduce routine handling but adds equipment cost and creates a dependence on replacement fleece.
Skimmer chamber
The chamber must fit the skimmer body, pump and cable while maintaining the manufacturer’s recommended water depth. An adjustable baffle is useful, but a skimmer stand may still be required.
Return chamber
Evaporation appears in the return chamber, so a very small chamber can expose the pump quickly if an automatic top-off fails. It must fit the return pump and sensors with room for cleaning.
Refugium or equipment space
A dedicated refugium can hold macroalgae or habitat for small invertebrates, but it should not be assumed to solve every nutrient problem. Some aquarists gain more value from using the chamber for a larger skimmer, media reactor or easier maintenance access.
Eshopps RS-100 5th Gen
Best for: a compact conventional sump with clear skimmer and return areas.
Eshopps currently lists fifth-generation RS models in several sizes. The RS-100 is a sensible comparison point for smaller reef systems, but buyers must use the fifth-generation specifications: the older RS-75 featured in the original article is discontinued, and dimensions from prior generations should not be mixed with current models.
Watch for: confirm the exact filter-sock arrangement, skimmer chamber and return chamber against your equipment. The display-tank range is only a starting point.
Trigger Systems Ruby30E
Best for: aquarists wanting a premium acrylic sump with adjustable working depth and organized accessory provisions.
Trigger Systems maintains several sump families. The Ruby30E represents its established conventional format and is supported by a model-specific manufacturer page. The layout provides separated working areas and an adjustable baffle, making it easier to match a skimmer’s operating depth.
Watch for: premium cable, probe and dosing provisions are useful only if they remain accessible inside the cabinet. Compare the exact Ruby30E dimensions with the stand opening and skimmer footprint.
Official Trigger Systems Ruby30E information
Fiji Cube Fiji-15 Advanced Reef Sump 2nd Gen
Best for: a compact cabinet where an adjustable skimmer depth and covered acrylic layout are valuable.
Fiji Cube’s current second-generation range includes multiple sizes. The Fiji-15 provides a compact complete-sump option, while larger models offer more working area. The range uses support bracing and covers intended to limit splashing, salt creep and evaporation.
Watch for: availability varies by model, so use the live manufacturer range and do not substitute dimensions from the sold-out Fiji-36 or the old DIY kit described in the former article.
Current Fiji Cube Advanced Sump range
IceCap 36 Reef Sump V2
Best for: a larger under-cabinet installation needing several functional zones.
The IceCap 36 V2 is a current complete sump with space intended for mechanical filtration, a protein skimmer, refugium use and the return pump. Its larger footprint can improve equipment access compared with compact sumps.
Watch for: large external dimensions are an immediate cabinet-fit constraint. Confirm that the sump can pass through the stand opening and that equipment can still be lifted out after installation.
Official IceCap 36 Reef Sump V2 information
Bashsea Signature Series SS-30
Best for: aquarists prioritizing robust construction, large drain handling and adjustable operating depth.
Bashsea documents the SS-30 as a 30 × 15 × 16-inch, two-section sump with an adjustable water gate, a 1.5-inch drain and a seven-inch sock. The manufacturer rates it for aquariums up to 120 gallons, but equipment fit and safe drain-down volume remain the deciding factors.
Watch for: the two-section design differs from sumps with a dedicated central refugium. Decide whether the open working area will hold your intended skimmer and accessories before purchase.
Official Bashsea Signature Series specifications
Fiji Cube DIY sump baffle kit
Best for: an experienced aquarist converting a compatible standard aquarium into a custom sump.
A baffle kit can provide more volume for the budget and lets the owner choose the chamber layout. Fiji Cube currently supports kits for selected standard aquariums, including 20-long, 29-gallon and 40-breeder formats.
Watch for: verify the donor aquarium’s internal dimensions, glass condition and compatibility with the exact kit. Follow the adhesive and curing instructions, leak-test away from livestock, and calculate drain-down volume before connecting it to the display.
Current Fiji Cube sump baffle kits
Safe installation checklist
- Use an overflow and drain design with appropriate redundancy; do not rely on an untested single siphon.
- Support plumbing so pipe weight does not twist bulkheads.
- Install unions and valves where they can be reached and serviced.
- Keep power supplies, controllers and connections away from splash zones, with drip loops and appropriate ground-fault protection.
- Mark the maximum safe operating level on the sump.
- Switch off the return pump and allow the entire system to drain fully during testing.
- Confirm that return outlets break siphon before the sump overfills.
- Test the emergency drain without livestock present.
- Never leave a newly started system unattended until water levels and plumbing are proven stable.
Frequently asked questions
How large should a reef sump be?
Use the largest sump that fits the cabinet, equipment and service space while retaining adequate empty drain-down capacity. Total volume is helpful, but chamber dimensions and safe freeboard are more important than a percentage rule.
Does a sump need a refugium?
No. A refugium can be useful, but many successful systems use the available space for skimming, mechanical filtration, reactors or easier maintenance. Choose the layout that serves the aquarium’s actual needs.
How high should the sump water level be?
The skimmer chamber should match the skimmer’s recommended operating depth, while the overall running level must leave enough empty volume for power-off drain-down. Test the finished system rather than relying only on calculation.
Why does the return chamber level fall?
Evaporation appears in the return section because the upstream baffles maintain the other chamber levels. An automatic top-off can stabilize salinity, but its sensor, reservoir and maximum delivery volume must be configured safely.
How we selected these sumps
We prioritized current manufacturer support, a range of cabinet sizes and layouts, published dimensions, service access and clear filtration roles. We removed the discontinued Eshopps RS-75, unsupported generic marketplace sumps, hang-on refugiums presented as complete sumps and old product listings that could not be verified. No temporary prices or unsupported star ratings are used.
