Aquarium Sump Anatomy Glossary Guide: Refugium Skimmer Return Sections
Aquarium sump anatomy in plain terms: a sump is a secondary tank positioned below the display, divided into chambers by glass baffles, that houses filtration equipment, hides heaters and skimmers, and adds water volume. A typical reef sump has three sections — skimmer chamber (water inlet), refugium (mid-section for macroalgae or carbon reactor), and return chamber (where the pump pushes water back to the display). Understanding aquarium sump anatomy properly lets you size baffles and return pumps correctly, which this Gensou Aquascaping guide from 5 Everton Park breaks down section by section.
The Skimmer Chamber
The first sump section receives water from the overflow drain. It must be sized to match skimmer footprint and depth — typically 250-300 mm wide and 200 mm water depth for mid-range protein skimmers. A bubble trap baffle assembly at the chamber exit prevents micro-bubbles from migrating downstream. The chamber’s water level must stay within ±5 mm of the skimmer’s rated depth, which means a constant-level outlet is essential.
Baffle Geometry and Dimensions
Baffles are glass partitions siliconed into the sump that direct flow between chambers. The classic three-baffle bubble trap has water flowing up-over-down-under-up to break bubble adhesion. Baffles space 25-40 mm apart and stand 50-100 mm shorter than tank rim. Spacing too narrow restricts flow; too wide leaks bubbles through. Baffle silicone bead must be 6-8 mm thick for a 10 mm glass sump.
The Refugium Section
The middle chamber typically houses macroalgae (chaetomorpha or caulerpa) under a refugium light, plus live rock or rubble. The refugium’s role is nutrient export — macroalgae absorb nitrate and phosphate, then get harvested fortnightly. Refugium chambers also serve as biological filtration via deep sand beds (DSB) at 100 mm depth. Browse the refugium light selection at Gensou.
The Return Chamber
The final chamber holds the return pump, auto top-off (ATO) sensor and any peripheral equipment. This section’s water level fluctuates with evaporation — typically 30-50 mm daily in Singapore HDB conditions. The ATO refills with RODI water as the level drops. The return pump pushes water back to the display through 3/4-inch flexible PVC hose.
Drain Plumbing and Return Lines
Drain plumbing runs from overflow to skimmer chamber via flexible vinyl or rigid PVC. Hose size scales with display volume — 25 mm ID for tanks up to 300 L, 32 mm for 300-600 L, 40 mm for 600+ L. Return lines run smaller (15-20 mm ID) and connect to the display via Loc-Line or rigid pipe with 45-degree return nozzles for circulation.
Return Pump Sizing
Target sump turnover at 5-8 times display volume per hour. A 200-litre display needs 1000-1600 L/h pump. Account for head loss — every 30 cm of vertical lift costs 10-15 per cent of rated flow. A 1500 L/h pump rated at 0 m delivers 1100-1200 L/h at the typical 1 m sump-to-display lift. DC pumps from Jebao, Sicce and Maxspect dominate the SGD 80-300 range.
Filter Sock Holders
Mechanical filtration in sumps uses 100-200 micron filter socks held by a slot-mounted PVC bracket at the drain inlet. Socks trap detritus before it reaches the skimmer. Replace or clean every 3-7 days — neglected socks become biofilm farms that release ammonia. Some sumps replace socks with reusable filter felt sheets or roller-mat systems.
Sump Sizing Rules
A good rule: sump size = 25-30 per cent of display volume. A 300-litre tank needs a 75-90 litre sump. Sumps too small flood during power-cuts; too large waste cabinet space. Always calculate “drain-down volume” — the water that siphons from display to sump when power cuts. Mark this safe-fill line during initial setup.
Singapore Cabinet and Build Notes
HDB cabinet dimensions constrain sump footprint. Most kitchen-cabinet-style stands accept sumps up to 90 cm wide and 45 cm deep. Custom sumps from local fabricators run SGD 200-450 depending on glass thickness and baffle count. The tank and cabinet section at Gensou includes pre-fabricated sump options sized for common display footprints.
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5 Everton Park #01-34B, Singapore 080005 · Open daily 11am – 8pm
