Red Sea Reefer S-850 G3 Black

• 850 L total system volume – 680 L display over a 170 L sump.
• Redesigned G3 plumbing – fewer 90-degree bends and a curved return outlet, which Red Sea states improves circulation and lowers running noise compared with the previous generation.
• ReefGate flow valve – precise control over the drain rate, aimed at near-silent overflow operation at a stable water level.
• Removable surface skimmer on the overflow box – built into the central overflow for easier maintenance access.
• 19 mm ultra-clear, rimless glass – Euro-braced and bottom-braced for structural rigidity without a full top rim.
• ReefATO+ auto top-off included – top-off, temperature monitoring and leak detection, standard across the G3 range.
• ReefMat-ready sump chamber – built to take Red Sea's automatic filter roller if you add one later.

• REEFER-S 850 G3 aquarium with integrated central overflow box and removable surface skimmer
• Marine-spec cabinet in black, aluminium-framed with plywood panels
• Glass sump with pre-glued plumbing, split main and multipurpose extension chamber
• 2 x 32 mm dual return-pump outlets
• 2 x 225-micron filter bags and media cups
• ReefATO+ auto top-off with temperature sensor and leak detector
• Slide-out control panel and ReefGate flow valve
• Levelling feet

• Return pump – sized and bought separately
• Protein skimmer – this is the base tier, not the MAX
• Lighting – no fixture or mounting arms fitted; see our aquarium lighting range
• Heater and any temperature controller
• Chiller
• Dosing pump system
• ReefMat automatic filter roller (though the sump chamber is built to take one)
• RO/DI unit and saltwater mix – the tank ships dry
• Live rock, sand, aquascape and livestock

"G3" and "REEFER-S 850" describe the tank, cabinet, sump and plumbing only. If a listing elsewhere says "MAX", that's a different, fully-equipped product at a different price point – this one is the base platform for you to equip yourself.

Red Sea hasn't published an empty or filled weight for this model. Water alone runs to roughly 850 kg at full volume before cabinet, glass, rock and sand are added – have the floor checked before it goes anywhere other than a slab or reinforced ground floor.

The move to G3 is a plumbing and flow redesign rather than a change in tank size or glass spec. Red Sea's own material for G3 states a redesigned flow system delivering up to 50% more water circulation at lower energy consumption, plumbing with fewer sharp 90-degree bends to cut turbulence and noise, a new ReefGate valve for precise drain control, curved return outlets for better distribution, and an enlarged downflow inlet to reduce turbulence. ReefATO+ auto top-off was standard from the G2+ revision onward and continues unchanged in role on G3. We haven't been able to confirm whether G2+ and G3 sump and plumbing spares are interchangeable – check with us before ordering a spare part across generations.

Suited to a reefer who wants Red Sea's quietest, highest-flow Reefer plumbing to date and is choosing their own return pump, skimmer and lighting. Not the right choice if you want equipment fitted out of the box – for that, ask us whether a MAX configuration of this model is available.

The removable surface skimmer on the overflow box is designed for easier routine cleaning than a fixed weir. Filter bags in the sump need regular changing unless a ReefMat roller is added; the ReefATO+ sensor and reservoir need periodic checks and top-ups with RO/DI water.

ReefATO+ and any equipment you add are mains-powered – run everything through an RCD-protected circuit with drip loops on cables entering the cabinet. Check the ReefGate valve setting after any plumbing work; an incorrectly set valve affects both noise and overflow water level.

Covered by Red Sea's manufacturer warranty – 3 years standard, extendable to 5 years at no extra cost by registering the tank with Red Sea online – in addition to your consumer guarantee rights under Australian Consumer Law. This is an oversized, heavy item; expect a two-person delivery and confirm doorway and stair clearance before ordering.

Does this include a return pump, skimmer or lights?

No – this base configuration includes the tank, cabinet, sump, plumbing and ReefATO+ auto top-off only.

What actually changed from the G2+ version?

Mainly the plumbing and flow design: Red Sea states up to 50% more circulation, a new ReefGate valve for quieter drain control, curved return outlets and a redesigned downflow inlet. Tank size, glass thickness and the ReefATO+ auto top-off are unchanged.

Is the sump ready for a ReefMat filter roller?

Yes – the sump chamber is built to take one, though the roller itself is sold separately.

How much does it weigh filled?

Red Sea hasn't published a filled weight for this model. Water alone is roughly 850 kg at full volume – get the floor checked before siting it anywhere other than a slab or reinforced ground floor.

Will G2+ spare parts fit this tank?

We can't confirm that either way – Red Sea maintains generation-specific spare parts listings, and we haven't found a source confirming shared parts between G2+ and G3. Check with us before ordering a spare part for this tank.