The 6 Best Aquarium Overflow Boxes

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Overflow boxes transport aquarium water to under cabinet sumps without having to drill the aquarium glass. These boxes make it possible to utilize an under aquarium sump, wet/dry filtration system or refugium, opening up more opportunities for a wider variety of filtration methods without having to drill the bottom of your aquarium.

When choosing your overflow box, make sure to get the right size box for your aquarium size. Using the right size return pump for your aquarium size and overflow box capacity is also extremely important. If a return pump with too high of a capacity is used, the tank may overflow and/or the sump may be drained.

Eshopps Inc. PF300 Overflow Box for Aquariums

Eshopps Overflow Box

Eshopps' overflow boxes feature bulkhead fittings for secure and convenient installation. Use these easy-to-install overflow boxes to transport aquarium water to under cabinet sumps, refugiums, or wet/dry filters. The gravity-feed system eliminates the need for complicated drilling or aquarium modifications.

  • Made of high-quality acrylic for durability and long life.
  • Six sizes are available for aquariums from 20 gallons to 300 gallons.

CPR Continuous Siphon Overflow

CPR Overflow Box

These pre-filters move water from an aquarium to a filtration system without tank modifications. CPR or continuous siphon overflow units skim up to six times more water than units with tubes. Can be hard plumbed with standard PVC pipe. (Does not include a lid.) Use of Aqua Lifter Pump is necessary to prevent trapped air from the siphon. Combine with Aqua Lifter Filter, a suction-style floss debris filter, to maximize efficiency and use of the Aqua Lifter Pump.

Blue Ocean 600 Overflow Box Continuous Siphon 125G Aquarium

Blue Ocean Overflow Box

The blue ocean 600 overflow box continuous siphon is designed for aquariums up to 125 gallons, overflowing up to 600 gallons per hour into your sump. This quality built overflow box in constructed of acrylic for a long, useful life and includes a 1-inch bulkhead fitting.

Aqueon ProFlex Hang-On Overflow Box Model 220 w/ Return Nozzle

Aqueon Overflow Box

The aqueon hang-on overflow boxes are constructed of high-quality acrylic to last for almost forever. Two sizes are available. The model 34508 is a single overflow for aquariums up to 125 gallons. The model 34509 is a dual overflow (2 in case one gets clogged up) and is designed to service tanks for up to 400 gallons.

KollerCraft TOM RP3 Overflow Box

KollerCraft TOM RP3 Overflow Box

The KollerCraft TOM RP3 Overflow Box is the Cadillac of overflow boxes. This overflow box provides easy connection to sump-style filters without aquarium modifications. The built-in anti-siphon feature prevents flooding during a power outage and automatically primes and starts water flow back to the filter when electrical power returns. The gravity-fed Venturi system automatically primes and initiates water flow to the sump filter quickly. It is capable of handling pumps with up to 800 GPH flow rate. This overflow box measures 8 x 7-1/2 x 6-1/2 inches (LxHxW) and mounts to tank frames up to 1.75 inches thick.

The KollerCraft TOM RP3 Overflow Box is designed to feed the KollerCraft TOM Rapids Pro RP3 Wet/Dry Filter System for a complete filtration system for saltwater aquariums up to 125 gallons.

Your Choice Aquatics OF-Overflow Box

Your Choice Aquatics OF-Overflow Box

Aquatics OF-overflow boxes are constructed of high-quality cell cast acrylic and are available in five sizes to service aquarium from 30 gallons to 180 gallons in size.

Each of these overflow boxes is of a self-priming design to begin functioning on its own in the event of a power failure. The surface skimming box includes a noise-reducing cylinder foam sleeve for easy-maintenance mechanical filtration and bulkhead fitting for a watertight operation.

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