BestForPets is reader-supported. Your purchases via our links may earn us an affiliate commission at no extra cost to you. Our Affiliate Disclaimer

The 6 Best Hang-On-Back Refugiums

If you've been thinking about getting into fish or shrimp breeding, or even rearing invertebrates like amphipods and copepods for aquarium food, you've probably heard about refugiums. Refugiums enable tank water to pass through while shielding ill or weak fish, as well as fry and shrimplets, from predation in the tank.

Refugiums are an excellent choice for quarantine and breeding, and some may even function as part of a sump system. However, learning about refugiums may be intimidating and complex, so BestForPets (bestforpets.org) has compiled evaluations of the best hang-on-back refugiums for your aquarium.


External Refugium Breeder Hang-On Box by Finnex

The Finnex External Refugium Hang-on Box is more than just a HOB refugium, making it the ideal all-around HOB refugium choice.

It also has an adjustable water pump and an LED light appropriate for medium to high lighting requirements. This kit is also available without a light and with a light appropriate for modest lighting demands.

This HOB refugium is constructed of strong plastic and is 10.25 inches by 5.5 inches by 5 inches. It comes with two leveling knobs to assist prevent spillage, however overflow is possible if the outlet becomes clogged.

This refugium also has detachable baffles to assist lower water flow even more if shrimp, fry, or low-flow fish like bettas require it. The integrated water pump has a flow rate of up to 40 gph.


  • Made of tough plastic
  • Water pump is adjustable.
  • LED light with medium to high requirements
  • It is available with both low-light LED and no light.
  • Leveling knobs are included.
  • It has detachable baffles.
  • The water pump may produce up to 40 gph.


  • If the outlet becomes clogged, it may overflow.
  • If no baffles are utilized, the lowest flow may be excessively powerful.


Fluval Holding and Breeding Box with Multiple Chambers

The Marina Hang-on Breeding Box is the greatest HOB refugium for the money. It can contain up to 12 gallons of water and has separators that can form up to three chambers.

The separators include slats just large enough for the fry to pass through in order to be separated from the mother.

This HOB refugium is constructed of strong, translucent plastic and is 10.7 inches by 5.8 inches by 5.7 inches. It is suitable for use with rimless aquariums with a minimum glass thickness of 5mm.

This HOB refugium comes with leveling feet and is also available in two smaller versions. It necessitates the use of an air pump, which is not provided.


  • 12 gallon water capacity
  • Separators are included to create up to three compartments.
  • Separators have slats that are large enough for fry to pass through.
  • Plastic that is both strong and translucent
  • Can be used in aquariums with no rims.
  • This includes leveling feet.
  • There are three sizes available.


  • An air pump is necessary, however it is not provided.
  • If the outlet becomes clogged, it may overflow.
  • For usage in rimless aquariums, 5mm thick glass is required.


AquaFuge2 Hang-On Refugium CPR

Consider the CPR AquaFuge2 Hang-on Refugium for a high-end option. This product is available in three sizes of strong acrylic. They have a black acrylic covering that prevents light from passing through to the main tank, making this product ideal as a plant refugium.

This HOB refugium’s biggest size choice is 25.5 inches by 4.5 inches by 12 inches and contains 4.7 gallons of water. This package contains a powerhead in each of the three sizes.

This device is constructed with baffles that allow plants, animals, and substrate in the refugium to stay undisturbed while preventing stagnant water.

This item does not have a light, but there is space above the water line for one. The baffles in this kit are not detachable, and there is no lid.


  • Acrylic is a strong material.
  • Available in three sizes ranging from 4.7 gallons to 4.7 gallons.
  • The black backing prevents light from leaking into the main tank.
  • It comes with a powerhead.
  • The unique baffles system prevents stagnation.


  • Premium cost
  • The baffles cannot be removed.
  • There is no light included.
  • No lid


External Plastic Aquarium Fish Breeding Box Satellite Hanging

The Sudo Starpet Hang-on Breeding Box is a huge and durable HOB refugium. It is essentially identical to the Marina HOB Breeding Box but costs more.

This HOB refugium does not come with an air pump or a light, although both are essential for usage, and a light is suggested. This HOB refugium is 10.7 inches by 5.8 inches x 5.7 inches and is made of strong, clear plastic with two leveling knobs.

It also has two separators with slats large enough for fry but not large enough for adult fish to get through. The slats may be used to divide the box into three distinct compartments.


  • 12 gallon water capacity
  • Separators are included to create up to three compartments.
  • Separators have slats that are large enough for fry to pass through.
  • Plastic that is both strong and translucent
  • This includes leveling feet.


  • An air pump is necessary, however it is not provided.
  • If the outlet becomes clogged, it may overflow.
  • Priced more than comparable items


Hang-On Separation Breeder Box ISTA IF-648

The ISTA IF-648 Hang-on Breeder Box is composed of translucent plastic that can be scratched if handled roughly. It can fit over an aquarium rim or edge up to 1 inch wide.

This HOB refugium is 10 inches by 5.5 inches by 5.25 inches in size and contains around 12 gallons of water. It features two dividers with slats that separate the fry from the other fish. This box may be used to create up to three chambers.

This product’s separators and holders allow for some customisation. The box lacks the necessary air pump and light, but it does have a top. The pump intake can be noisy and may need to be adjusted to decrease noise.


  • 12 gallon water capacity
  • Fry can travel through removable dividers with slats.
  • Separators may be inserted in various positions, enabling three compartments to be customized.
  • There is a lid included.
  • This includes leveling feet.


  • Rough handling may cause scratching.
  • Only fits over 1″ rims.
  • An air pump is necessary, however it is not provided.
  • The pump inlet may be noisy and necessitate changes.


Aquarium Filter Blue Ocean REF 15 Hang On

The Blue Ocean REF 15 Hang on Refugium is a high-end acrylic HOB refugium. It has a black acrylic back to prevent light from escaping into the main tank.

It is prone to scratching and portions may break when handled roughly. It is also prone to leaking, so keep an eye out for this.

This item is 13.25 inches by 4.75 inches by 12 inches and contains approximately 12 gallon of water. It does come with a filter and a bio sponge intake cover.

It does not have a light. If this product chips or cracks, aquarium-safe epoxy or acrylic can be used to fix it. It merely has one chamber and is devoid of baffles.


  • Approximately 12 gallon capacity
  • The black acrylic backing stops light from leaking into the main tank.
  • Filter with bio sponge input cover is included.
  • If necessary, chips and cracks can be fixed.


  • It readily scratches and breaks.
  • Susceptible to leaking
  • There is no light included.
  • There is no cover.
  • No baffles or separators in a single chamber


Because it is a high-quality product that contains everything you need to get a HOB refugium up and running, the Finnex External Refugium Hang-on Box is the best overall HOB refugium selection.

The CPR Aquafuge2 Hang-on Refugium is the best premium choice since it is composed of high-quality materials and comes with a fully working pump system.

The Marina Hang-on Breeding Box is the best value because it’s high-quality, inexpensive, and especially beneficial if you already have a pump and light at home.

Choosing a HOB refugium may be daunting, and learning everything there is to know about getting a HOB refugium to function can be complicated, so use BestForPets‘ (bestforpets.org) list of goods to help you choose the best hang-on-back refugiums so you can focus on how you want to set it up to work best for your tank.

Buyer's Guide

Your Intention

Consider what you want to use your HOB refugium for before selecting one for your tank. Some HOB refugiums are best used as a basic breeder box, while others are ideal for use as a fully working sump system.

Some boxes may be more suitable for breeding fish rather than shrimp, while others may be better suited for producing algae and amphipods.

Your Tank Configuration

If your tank is on a tight light cycle and you’re growing high-light algae in a HOB refugium, choosing a box with darkish backing will assist prevent light flow into your aquarium.

If the water in your tank is cooler than what you’re rearing, breeding, or growing in the HOB refugium, you’ll need to consider installing a heater to warm the water for the refugium without heating the tank.

The Glass in Your Tank

If you have a tiny rimless tank, a 12 gallon HOB refugium will be too hefty and risk cracking or fracturing the glass. If you have a tiny tank with a strong rim, it will be able to hold a heavy box.

Knowing the thickness of your tank’s glass and the width of its rim, if one exists, can assist you in selecting the best HOB refugium for your tank.

Options for HOB Refugium

Refugium box versus. kit: Which is better?

If you’re not sure how to set up a HOB refugium or simply want something simple, buying a kit could be the best solution for you. A kit should include all or most of the equipment needed to get your HOB refugium up and running.

If you are confident in your abilities to set it up, or if you have supplementary equipment, such as air pumps, that you need to utilize, then purchasing a HOB refugium box without all the bells and whistles should suffice.

Separators vs. baffles vs. single chambers

You may prefer a single chamber box depending on your intended HOB refugium application. If you wish to utilize a HOB refugium as a breeder box for fish that will consume fry, a box with slotted separators may be ideal.

Separators are also a good alternative if you need to keep many fish out of the main tank, such as during quarantine, although they will fight in close quarters.

Baffles are a sort of divider with varied size slots, some of which are fully solid, and may be put at different heights in the box.

If you want to utilize a HOB refugium for a sump system, baffles are an excellent technique to guide and filter water movement. Baffles can also protect fragile plants and corals from the passage of water.

Plastic vs. acrylic

Acrylic is technically a plastic, but not all plastics are made equal. Acrylic is a thick, robust plastic that is strong but inflexible, rendering it susceptible to cracking when subjected to excessive pressure or harsh treatment.

Other forms of plastic can be thinner and weaker than acrylic, but more flexible, which means they are more likely to shatter over time but less likely to fracture.

Because acrylic is easier to repair than other types of plastic, a higher-quality HOB refugium will most likely be fashioned of it.

Clear versus darker backing

How much light do you want to transmit through the main tank to the HOB refugium? Because some boxes have clear backing, whatever light you put into the refugium will leak into the main tank, and vice versa.

If you want certain light requirements to be satisfied within the main tank or the HOB refugium, a darker backing will likely fit your tank’s demands better since it allows you to retain separate lighting for your main tank and your HOB refugium.

Lid versus no lid

HOB refugiums are available with or without a lid, as well as with a lid that may be purchased separately. This is entirely dependent on your requirements for your HOB refugium. A box without a lid will evaporate more than a box with a lid.

A box with a lid regulates temperature better than a box without a cover. Some individuals prefer a HOB refugium without a cover for simplicity of maintenance, cleaning, and access to plants or animals if necessary.

When deciding whether or not to purchase a HOB refugium with a cover, consider your family size. Small children may be tempted to put their hands into a box that does not have a lid.

Some pets may be prone to drinking from a box without a cover or attempting to trap creatures within.


The size of your HOB refugium will be determined totally by your preferences, tank size, and intended use. Your tank’s glass and rim must be able to hold the weight of whatever HOB objects you place on them.

If you want to put up a sump refugium, you will most likely require a big HOB refugium. A smaller HOB refugium may fulfill your needs if you need a temporary holding room for acclimating new fish to the tank or safeguarding sick fish.

HOB refugiums are available in a variety of sizes, giving you lots of alternatives to match your needs.

Author Image

Dr. Deborah Fletcher

Deborah R. Fletcher, DVM, is a skilled veterinarian with more than 15 years of experience dealing with companion and exotic animals. She has experience caring for a variety of animals, including household cats and dogs, reptiles, birds of prey, and even primates. Dr. Fletcher is a valuable part of the BestForPets team, where she contributes to their aim of providing pets and their owners with the finest possible treatment and services.

Veterinarian (DVM) Dr. Deborah Fletcher


0.0 out of 5 stars (based on 0 reviews)
Very good0%

There are no reviews yet. Be the first one to write one.

Related articles