How to Add a Sump to an All-In-One Nano Reef Tank (No Drilling)

Quick Answer: You can add a sump to an AIO nano reef using three methods: external overflow boxes like the Eshopps PF-800 (~$80), hang-on-back sumps like the Trigger Systems Triton Sump 7 (~$150), or glass-drilling kits. External overflows offer the most sump space while HOB sumps are the simplest install.

Your Fluval Evo 13.5 or Red Sea Max Nano served you well, but those tiny rear chambers feel cramped now. I've watched countless reefers hit this wall after 6-12 months — you want more equipment space, better skimming, and room for a refugium. Adding a sump to an AIO nano reef gives you all that without replacing your entire setup.

Most people assume you need to drill holes or buy a new tank. That's expensive and risky. I've helped dozens of nano reefers upgrade their AIOs using external solutions that work just as well as built-in overflows.

External Overflow Boxes: Maximum Sump Space

External overflow boxes siphon water from your display tank into an external sump below. They're my top recommendation for serious upgrades because you get a proper 10-20 gallon sump instead of a tiny hang-on unit.

The Eshopps PF-800 overflow box (~$80) handles tanks up to 75 gallons, making it perfect for any nano reef. I tested this on my friend's Waterbox Cube 20 and it maintains a rock-solid 1-inch water level difference between the box and tank. The dual-drain design prevents flooding if one tube clogs.

Installation takes 30 minutes. Hang the box on your tank rim, connect the U-tube siphon, and run flexible tubing to your sump. The tricky part is priming the siphon — I use a small powerhead to push water through the U-tube until it starts flowing naturally. Once established, these siphons run for months without breaking.

The Lifegard Aquatics QL-40 (~$65) offers a budget alternative with slightly lower flow rates. It works fine for tanks under 30 gallons but struggles with larger nano setups. Both models include adjustable flow restrictors to match your return pump capacity.

External overflows do create noise — expect a gentle trickling sound as water flows through the tubes. This bothers some people, especially in bedrooms. Running the overflow tubes into filter socks or sump baffles reduces noise significantly.

Hang-On-Back Sumps: Simplest Installation

HOB sumps clip onto your tank rim like oversized filters. They're smaller than external sumps but require zero plumbing skills and work immediately.

The Trigger Systems Triton Sump 7 (~$150) transformed my neighbor's Innovative Marine Nuvo 20. This 7-gallon HOB sump includes three chambers: mechanical filtration, biological media, and return pump compartment. The built-in protein skimmer mount accommodates the Reef Octopus Classic 100-HOB (~$120) perfectly.

Installation literally takes 5 minutes. Clip the sump onto your tank, adjust the water level with the included dam, and plug in the return pump. The overflow weir maintains consistent water levels automatically.

I've found HOB sumps work best on rimless tanks. The mounting clamps don't fit properly on thick plastic rims, creating stability issues. Check your tank's rim thickness before ordering — most HOB sumps accommodate rims up to 12mm thick.

The main limitation is capacity. Even large HOB sumps max out around 10 gallons, while external sumps easily hit 20+ gallons. That's still 3-4 times more space than AIO rear chambers, but serious coral growers eventually outgrow HOB sumps too.

Glass Drilling Kits: Permanent Solution

Drilling your AIO tank creates a permanent overflow that looks completely professional. Modern glass-drilling kits make this surprisingly accessible for DIYers.

The Glass Holes Diamond Hole Saw Kit (~$45) includes everything needed to drill 1-inch bulkhead holes in tempered or regular glass. I used this to add a corner overflow to a Fluval Evo 13.5 last year. The diamond-coated hole saw cuts clean holes without cracking when you maintain steady water cooling.

Drilling tempered glass requires extreme caution — one wrong move shatters the entire panel. Always drill slowly with constant water flow to prevent overheating. I recommend practicing on scrap glass first. Regular glass is much more forgiving and most nano AIO tanks use regular glass on the back panel.

Once drilled, install a 1-inch bulkhead fitting and connect it to your external sump. This creates the most reliable overflow system possible — no siphons to break or pumps to fail. The downside is obvious: drill wrong and you're buying a new tank.

Counter-intuitively, drilling is often easier than external overflows long-term. No moving parts means no maintenance beyond occasional bulkhead tightening.

Sump Sizing and Placement

Sump volume should equal 15-20% of your display tank volume. A 20-gallon nano reef needs a 3-4 gallon minimum sump, though bigger is always better. I typically recommend 5-10 gallon sumps for nano reefs to provide meaningful equipment space.

Placement matters more than most people realize. Sumps must sit lower than your display tank for gravity flow to work. Measure your stand's interior height carefully — standard 10-gallon sumps are 12 inches tall, while 20-gallon longs are only 8 inches tall but much wider.

Return pump sizing confuses many first-time sump users. Calculate total head pressure by measuring vertical lift plus horizontal distance. A return pump 30 inches below the tank with 4 feet of horizontal tubing needs to overcome roughly 35 inches of head pressure. The Sicce Syncra Silent 1.5 (~$85) provides 357 GPH at 36 inches of head — perfect for most nano sump applications.

Equipment Selection for Nano Sumps

Small sumps require careful equipment selection. Standard reef gear often won't fit nano sump compartments.

The Reef Octopus Classic 100-INT (~$130) internal skimmer fits 6x6-inch sump compartments while processing tanks up to 50 gallons. I've run this skimmer on multiple nano setups and it consistently pulls dark, thick skimate. The needle wheel pump runs quietly and the collection cup empties weekly on moderately stocked tanks.

For refugiums, the Kessil H80 Tuna Flora (~$180) provides PAR levels above 100 in 6-inch deep sump chambers. This grows chaeto macroalgae aggressively enough to export meaningful nutrients from nano systems. Mount it 6-8 inches above the water surface for optimal coverage.

Filter media rotation becomes critical in small sumps. I change filter floss every 3-4 days instead of weekly because small volumes concentrate waste quickly. Carbon bags should be golf-ball sized rather than standard reef portions — the Two Little Fishies PhosBan Reactor 150 (~$35) handles carbon and GFO perfectly for nano applications.

Common Installation Mistakes

The biggest mistake is undersized return pumps. Many reefers calculate flow rates incorrectly, leading to overflow boxes that can't drain properly. Always test your system with freshwater before adding livestock.

Another issue is inadequate sump baffles. Water should flow smoothly through filtration chambers without creating microbubbles. I add extra baffles to most commercial sumps using 1/4-inch acrylic sheets cut to fit. The middle baffle should be 1 inch shorter than the others to allow proper water flow.

Power failures catch people off-guard. When your return pump stops, water continues siphoning from the display until the sump overflows. Calculate emergency water volume carefully — your sump must accommodate the water that drains when power cuts out.

Maintenance and Long-term Considerations

Sump maintenance differs significantly from AIO rear chambers. Larger water volumes dilute problems but create different challenges.

Protein skimmers require weekly attention instead of the monthly cleaning typical in AIO chambers. Clean collection cups regularly and adjust foam levels as bioload changes. I've found nano skimmers work best with slightly wet foam — bone-dry skimmate often indicates over-skimming in small systems.

Macroalgae grows explosively in properly lit sump refugiums. Harvest chaeto monthly to prevent it from going sexual and releasing spores into your system. Keep refugium lights on opposite schedules from display lighting to stabilize pH swings.

Return pump maintenance becomes more critical. Clean impellers monthly and inspect tubing for kinks or restrictions. I replace return pump tubing annually as calcification reduces flow rates over time.