Updated August 2026
There are two winners because a hang-on-back filter and a hang-on-back refugium do different jobs. My favorite compact power filter is the AquaReady HOB-PF. My favorite true hang-on-back refugium is the AquaReady HOB-R. Choose the job first, then make sure the equipment physically fits behind your aquarium.
AquaReady HOB-PF
Compact, simple, and sized for aquariums up to 30 gallons. The large drop-in media basket gives you room to customize mechanical, biological, or chemical filtration.
Best for: Standard nano aquariums that need a complete everyday power filter.
Check the HOB-PF price at BRS
AquaReady HOB-R
A dedicated place to grow macroalgae and shelter pods without adding a sump. The Sicce feed pump is included, but the refugium light is not.
Best for: Aquariums 20 gallons and larger with at least 17 inches of tank length.
Check the HOB-R price at BRSFive hang-on-back filters and refugiums compared
These products are not interchangeable. Two are dedicated refugium solutions, two are traditional power filters, and one combines power filtration with a small protein skimmer.
| Product | Type | My pick for | Current fit | Main trade-off |
|---|---|---|---|---|
| AquaReady HOB-PF | Power filter | Best HOB filter for beginners | 5–30 gallons | Mounting plastic needs careful handling |
| AquaReady HOB-R | Refugium | Best universal HOB refugium here | 20+ gallons; 17-inch minimum tank length | Light sold separately |
| UNS Dual AIO Refugium | AIO refugium insert | UNS Dual AIO owners | UNS Dual AIO aquariums only | Not a universal accessory; light sold separately |
| AquaReady HF-M | Complete HOB filtration | Standard tanks needing filtration plus skimming | 20–60 gallons | Large and unnecessary on most AIO tanks |
| Seachem Tidal 55 | Power filter | Simple, proven filtration | Up to 55 gallons | Less compact than the HOB-PF |
Do you need a power filter or a refugium?
A power filter moves aquarium water through media. It can hold mechanical foam, biological media, activated carbon, or other media you replace and maintain. For a bare standard aquarium without built-in filtration, this is usually the first piece of equipment you need.
A refugium creates a protected growing area. Most beginners use it for Chaetomorpha or another macroalgae that consumes nitrate and phosphate as it grows. It can also provide shelter for copepods and other small life. A refugium is supplemental filtration; it does not replace the everyday mechanical and biological filtration your tank still needs.
If you already own an all-in-one aquarium with rear filtration chambers, you may need neither product. Do not hang more equipment on the tank unless it solves a specific problem.
How I chose these HOB filters and refugiums
I compared the job each product performs, how much room it occupies behind the aquarium, pump inclusion, media access, lighting requirements, tank and rim compatibility, maintenance access, and whether it makes sense on the beginner aquariums I recommend.
I like its compact body and generous media basket. It is a simple workhorse, although I have learned to handle the rim-mounting plastic carefully.
This is my dedicated refugium pick. It includes the feed pump, gives macroalgae real growing space, and leaves the light choice to you.
Both work, but for different builds. The HF-M is an entire filtration system; the Tidal is a straightforward power filter.
I like the purpose-built design and want to try it, but I am not presenting it as a universal refugium or as a product I have tested.
1. AquaReady HOB-PF Power Filter
My experience: I have used this filter. It is compact, effective, and simple to maintain. I have also broken the mounting plastic before, so I would install and adjust it carefully.
The compact workhorse for a standard nano aquarium
5–30 gallons
8 × 5.75 × 8 inches
Sicce Syncra Nano, 110 GPH
3.625 inches
- The drop-in media basket is large and easy to customize.
- The removable divider lets you organize different filtration media.
- The included Sicce pump is quiet, dependable, and energy efficient.
- The clear lid also allows the filter to be adapted into a small refugium.
What to know first: The filter must sit level, and the mounting area deserves a gentle hand. Do not force the plastic over a rim or overtighten the leveling hardware. Measure the rear and top clearance before pushing the aquarium against the wall.
My verdict: This is the HOB power filter I would buy for a beginner standard aquarium up to 30 gallons. It gives you useful media capacity without taking over the entire back of the tank.
Watch my AquaReady HOB-PF power filter walkthrough:
2. AquaReady HOB-R Hang-on-Back Refugium
My experience: I have used the HOB-R. It provides real room for macroalgae without requiring a sump, and I like that the included pump makes the water side of the installation straightforward.
A true external refugium for tanks without a sump
20+ gallons; 17-inch minimum length
16.75 × 3.25 × 12.75 inches
0.75 inch
Sicce Nano, 110 GPH
- The clear viewing panel lets you monitor macroalgae growth.
- The internal baffles support controlled flow and provide room for additional media.
- The outlet sponge reduces bubbles and trickling noise.
- Running the refugium light opposite the display-light schedule can help balance the system.
What to know first: A refugium light is required and is not included. The HOB-R is also physically large. Confirm tank length, rim thickness, wall clearance, and access for maintenance before buying it.
My verdict: Choose the HOB-R when you specifically want macroalgae and pod habitat on a sump-free aquarium. Do not buy it when a compact power filter is the problem you are actually trying to solve.
Watch my AquaReady HOB-R hang-on-back refugium walkthrough:
3. Ultum Nature Systems Dual AIO Refugium
My experience: This is the only main product in the guide I have not used. I like the design and want to get my hands on one, but this recommendation is based on its current specifications and purpose-built fit.
A clever insert—when you own the matching aquarium
UNS Dual AIO aquariums
8.35 × 3.15 × 2.68 inches
- It converts part of the existing rear filtration chamber into a protected refugium.
- The opaque housing helps contain light spill into the display.
- An adjustable clamp secures the insert in the matching filtration chamber.
- The dedicated light slips into the system cleanly instead of requiring a homemade mount.
What to know first: Despite the tempting dimensions, this is not marketed as a universal rear-chamber refugium. It is designed for UNS Dual All-In-One aquariums. The light is sold separately.
Matching accessory: UNS Mini Refugium Light
The 10-watt light has an inline controller and is designed to slip into the UNS refugium system. It is not included with the refugium.
Check the UNS light price at BRSMy verdict: If you own a compatible UNS Dual AIO, this looks like the cleanest refugium option in the guide. Everyone else should treat it as incompatible unless UNS or the retailer confirms otherwise.
Check the UNS refugium price at BRS4. AquaReady HF-M Complete Filtration System
My experience: I have used this system. I think of it as a power filter with an integrated protein skimmer and extra media capacity—not as a simple HOB filter.
For a bare standard aquarium that needs everything
20–60 gallons
16.75 × 3.25 × 12.75 inches
18 inches
0.75 inch
- It combines protein skimming, biological media, and a customizable media chamber.
- The included pump makes it a complete filtration package.
- Probe, tubing, dosing-line, and cord holders help organize a DIY build.
- It can turn a basic glass aquarium into a more capable saltwater system.
What to know first: This system is large and bulky. I would use it only on an aquarium without a sump or rear filtration wall. On an all-in-one aquarium, it duplicates equipment you already own and adds a lot of visible hardware.
My verdict: Buy the HF-M when you are starting with a bare standard aquarium and want power filtration plus a little skimming. Skip it when your tank already includes rear filtration chambers.
Watch my AquaReady HF-M complete filtration system walkthrough:
5. Seachem Tidal 55 HOB Power Filter
My experience: I have used the Tidal. It is not fancy, but it works. Seachem makes dependable aquarium products, and this is the straightforward choice when you want proven power filtration.
Large media capacity without plumbing
Up to 55 gallons
250 GPH
8.06 × 6.125 × 8.375 inches
3.5 inches
- The large basket can hold mechanical, biological, and chemical media.
- Flow is adjustable, and the intake depth can be changed.
- A surface-skimming inlet helps pull floating debris into the filter.
- Foam and Seachem Matrix biological media are included.
What to know first: The Tidal 55 is larger and more powerful than many nano tanks need. Seachem sells multiple Tidal sizes, so match the model to the aquarium rather than automatically buying the 55.
My verdict: Choose the Tidal when you want a conventional, adjustable power filter with generous media capacity. For the smallest beginner tanks, I prefer the more compact AquaReady HOB-PF.
Check the Tidal 55 price at BRSMeasure the tank and the wall clearance before you buy
Hang-on equipment needs more than a matching gallon rating. Measure the tank rim thickness, uninterrupted tank length, distance from the back glass to the wall, clearance above the aquarium, and the space needed to lift out a media basket or refugium algae. Check that the intake reaches the operating water level and that the equipment will not collide with a lid, light mount, return nozzle, or rear filtration wall.
Also plan for a power outage. Confirm the filter or refugium restarts correctly, that the aquarium can accept any drain-back water, and that every hose and fitting is secure. Leave a drip loop in every power cord.
Which HOB filter or refugium should you buy?
Start with the job your aquarium needs. On a phone, swipe inside the table to see every column.
| Product | Buy it when | Avoid it when | Placement | My experience | Buy |
|---|---|---|---|---|---|
| AquaReady HOB-PF | You need compact everyday filtration on a 5–30 gallon standard tank | Your aquarium already has good rear filtration | Hang on back | Personally used | Check BRS price |
| AquaReady HOB-R | You want a real macroalgae refugium without a sump | You lack 17 inches of tank length or room for a separate light | Hang on back | Personally used | Check BRS price |
| UNS Dual AIO Refugium | You own a compatible UNS Dual AIO aquarium | You need a universal rear-chamber refugium | Matching UNS rear chamber | Not personally used | Check BRS price |
| AquaReady HF-M | A bare standard tank needs filtration and a small skimmer | You already own an all-in-one aquarium | Hang on back | Personally used | Check BRS price |
| Seachem Tidal 55 | You want conventional filtration, adjustable flow, and a large media basket | A smaller Tidal or the compact HOB-PF better fits the tank | Hang on back | Personally used | Check BRS price |
Hang-on-back filter and refugium FAQ
What is the best hang-on-back filter for a saltwater aquarium?
My beginner pick is the AquaReady HOB-PF for a standard aquarium up to 30 gallons. It is compact, includes a dependable Sicce pump, and has a useful media basket. For a larger tank, consider the appropriately sized Seachem Tidal.
What is the best hang-on-back refugium?
My pick is the AquaReady HOB-R when the aquarium is at least 20 gallons, has 17 inches of available length, and can accept its 0.75-inch maximum rim. The pump is included, but you must add a refugium light.
Can a refugium replace a power filter?
Usually not. A refugium is best treated as supplemental biological filtration and nutrient export. A standard aquarium still needs adequate water movement plus mechanical and biological filtration.
Do I need a refugium on a beginner reef tank?
No. Regular water changes, appropriate feeding, good mechanical filtration, and sensible stocking can maintain many beginner tanks. Add a refugium when you specifically want macroalgae nutrient export or protected pod habitat.
Does the AquaReady HOB-R include a light?
No. It includes the Sicce Nano feed pump, but the macroalgae light must be purchased separately.
Will the UNS Dual AIO Refugium fit any all-in-one aquarium?
No. The current product is designed for Ultum Nature Systems Dual AIO aquariums. Do not assume it fits another rear chamber simply because the published dimensions appear compatible.
Can I use a hang-on-back filter on a rimmed aquarium?
Only when the mounting design accommodates the rim. Check the manufacturer’s maximum rim thickness and the space needed for the intake, leveling hardware, lid, and media access before buying.
Build filtration around the tank you actually own
Use the saltwater aquarium maintenance guides to decide whether the tank needs more nutrient control first. If you need stronger organic-waste removal, compare the nano and HOB protein skimmer guide, or return to the complete Gear Guide library.
