Designing a sump for your reef aquarium can feel intimidating, but once you understand the basics, it becomes one of the most rewarding parts of your system. A well-planned sump increases water volume, hides equipment, improves filtration, and makes maintenance easier. Let’s walk through the core elements of sump design so you can build (or refine) a setup that fits your tank and your goals.

Core Sections of a Reef Sump

Most reef sumps follow a simple layout divided into functional chambers. The exact order can vary, but these are the key sections you’ll want to plan:

1. Drain and Mechanical Filtration Section

This is where water first enters the sump from the display overflow.

• Filter socks or roller mat: Capture detritus and uneaten food before they break down.
• Noise control: Use flexible tubing, proper standpipes, and ensure drains enter below the waterline to reduce splashing.
• Easy access: Make sure you can remove socks or service your roller mat without contorting under the stand.

2. Skimmer and Filtration Chamber

The next section usually houses your protein skimmer and optional media reactors.

• Consistent water depth: Skimmers perform best at a stable water level. Use baffles or a skimmer stand to maintain the manufacturer’s recommended depth.
• Room for upgrades: Leave extra space for future gear like a refugium light, reactor, or UV return line.
• Good flow, not a torrent: You want fresh water passing through, but not so fast that your skimmer can’t process it effectively.

3. Refugium (Optional but Highly Recommended)

A refugium can help with nutrient export, microfauna production, and pH stability.

• Lighting: Use an appropriate spectrum for macroalgae and consider a reverse light cycle to help stabilize pH.
• Controlled flow: Moderate flow helps macroalgae grow while keeping detritus from settling.
• Barrier protection: Use a baffle with teeth or a screen to keep algae from clogging the return pump.

4. Return Pump Chamber

This final section sends water back up to your display tank.

• Auto top-off (ATO): Always place your ATO sensor here, since this is where evaporation shows.
• Enough volume: Size this chamber so that, if your ATO fails for a day or two, the pump won’t run dry.
• Back-siphon safety: Test a power outage to confirm the sump can hold the extra water that drains from the display.

Key Design Tips for a Quiet, Reliable Sump

Plan your sump around maintenance first. If it’s easy to clean and access, you’re far more likely to keep it running smoothly.

• Size matters: Aim for a sump that’s at least 25–40% of your display volume if space allows.
• Use baffles wisely: Three-baffle bubble traps (over–under–over) help keep microbubbles out of the return section.
• Cable and hose management: Label cords, route lines neatly, and keep drip loops below outlets.
• Plan for salt creep: Use lids or splash guards in high-turbulence areas.
• Think ahead: Leave a bit of extra space for future equipment or a larger skimmer.

If you’re still deciding on equipment, you may find our guides on choosing a protein skimmer and reef tank return pump sizing especially helpful while planning your layout. For a broader view of system planning, check out our reef tank plumbing basics article.

A thoughtfully designed sump turns your stand into a powerful filtration hub instead of a cluttered mess. By breaking the sump into clear sections, controlling water levels with baffles, and leaving room for future upgrades, you’ll create a system that’s quiet, stable, and easy to maintain—so you can spend more time enjoying your reef and less time wrestling with equipment.