A Hang-On-Back filter or Powerfilter as they are also known by are very popular in freshwater aquariums at providing a simple, easy-to-use and easy-to-clean filter, but how well do they work with a saltwater aquarium?
“Saltwater aquariums need high-tech, top-of-the-line equipment, Right?” Wrong!
You can easily run a small saltwater aquarium with very basic equipment. You just need to understand its limitations and the work you have to do to maintain it for success.
A Hang-On-Back (HOB) or Power Filter can be used on smaller saltwater aquariums with Live Rock & a Protein Skimmer to provide the 3 means of filtration required for a healthy reef tank. HOB filters are mainly used for housing chemical filter media.
Many successful saltwater aquariums are run using HOB filters and correct selection, sizing and setup will ensure a good start to your reefing journey! Read On to find out more…
What is a HOB or Power Filter?
A HOB or Hang-On-Back Filter is exactly what it sounds like. It is an aquarium filter that hangs on the side or back of an aquarium.
The general way in which these filters work is to suck up water from the aquarium, pass that water through the filter media and then return it back to the aquarium.
The media that is placed in these filters can be changed to suit the aquarium or the operation.
HOB filters also make great little Refugiums for nano aquariums with the simple addition of some Cheato Macroalgae and a grow light.
How To Use A HOB Filter On a Reef Tank
At the start of the article I mentioned how you can use a HOB ‘With’ Live Rock & a Protein Skimmer, this is because a HOB filter does not provide enough filtration on its own to cope with the filtration demands of a saltwater aquarium.
There are 3 forms of filtration that you have to meet for your aquarium to maintain an ecological balance:
1. Mechanical Filtration
This is the capture and removal of large particulate matter and organic compounds. In a saltwater aquarium, this is usually taken care of by:
- Filter Floss
- Filter Sponges
- Filter Socks
- Roller Mat
- Protein Skimmer
- A combination of the above
2. Chemical Filtration
This is the capture and absorption or conversion of microscopic particulate matter. In a saltwater aquarium, this is usually taken care of by:
- Activated Carbon
- Chemi-Pure Elite
- Granular Ferric Oxide (GFO)
- A combination of the above
3. Biological Filtration
This is the growing and reproduction of bacteria used to process toxins. In a saltwater aquarium, this is usually taken care of by:
- Filter Sponges
- Ceramic Pieces
- Colonizing Material – MarinePure
- A combination of the above
Most HOB filters will come with a series of filter media designed to meet the needs of each type of filtration.
In a saltwater aquarium, these media are just not enough to successfully process all the waste that a reef tank produces. The main reason why there is so much more waste in a saltwater aquarium, compared to their freshwater counterparts, is the number of living organisms in a reef tank.
To cope with the processing of all this matter you need to use a HOB filter as part of the total filtration package. As well as your HOB filter, you are going to require the following:
Sand – Either Dry Sand or Live sand. Over time your Dry Sand will grow Nitrifying Bacteria and become Live Sand. This is will become part of your Biological Filter as your aquarium cycles.
Rock – Either Dry Rock or Live Rock. Just like the sand, it will become colonized over time and become the MAIN area for your Nitrifying Bacteria to colonize and become part of your Biological Filter.
Protein Skimmer – This will be your main method of Mechanical Filtration by removing organic particulate from the water.
The best way to set up your HOB filter to aid in helping these above filters is to:
- Remove and dispose of the media that came with the filter.
- If you don’t have much Live Rock add some MarinePure Gems to the filter to increase surface area for Nitrifying Bacteria to colonize.
- Insert a bag of Chemi-Pure Elite to provide chemical filtration. Chemi-Pure is a mix of Activated Carbon, GFO & Ammonia/Nitrite/Nitrate absorbing material.
- Place filter floss on the top as a mechanical filter.
By using the filter media mentioned above they work really well for smaller aquariums, last a long time and you can fit them in small areas – Perfect for HOB filters!
If you have plenty of live rock than the HOB filter will just be a holding vessel for the Chemi-pure and the filter floss.
If you have a larger aquarium and you have additional space on the back wall to add more equipment, you could consider adding a second HOB filter to give extra holding space for MarinePure media, additional filter floss or even converting it to a Refugium to hold MacroAlgae.
To find out even more about what each of the filter media mentioned above does and what is a refugium see the further down and in the links in the ‘Further Reading’ section at the end of this article.
Cautions To Be Aware of with HOB Filters
Although HOB Filters can be a great starter filter to your new aquarium there are a few cautions you have to be aware of to ensure it works at its best.
The sponges that come with the HOB filter really need to be discarded and never used. Sponges are notorious for trapping detritus and particulate matter.
As this matter breaks down they release Nitrates and Phosphates into your water. Even with diligent cleaning, it is hard to purge all the waste matter from the sponge. This is why sponge material is very rarely used in the saltwater side of the hobby.
Using Ceramic Media
Just like sponges, the ceramic media can trap detritus if not washed regularly (When I say washed, that is not washed under a tap! That will kill all the Nitrifying Bacteria on it – Wash it in a bucket of saltwater!)
The surface area of the ceramic pieces is also not that large. By swapping out the ceramic pieces with $13.00 worth of MarinePure Gems you are massively increasing the surface area on which your Nitrifying Bacteria can colonize.
More surface area for a given space will help process waste better and allow for higher bio-loads = More livestock 😉
The bio-wheels on some HOB filters are designed to provide additional surface area for Nitrifying Bacteria to colonize, but if you have lots of Live Rock or MarinePure Gems they are not required – Just remove them.
The additional problems that the bio-wheels can create is salt creep. Any splash from saltwater leaves behind the salt as it evaporates. This can build up over time and cover screens, glass tops, light bulbs, and the water spill-way from the filter.
This is one of the biggest reasons why many aquarists will not use a HOB filter once they upgrade. To keep a HOB filter working efficiently and prevent the build-up of detritus it could need cleaning every couple of days.
The filter floss can quickly become clogged if you feed heavy or have an overstocked aquarium and this can lead to a filter overflowing. You also need to remove all the filter media each week to suck up the detritus that collects in the bottom of the filter.
A turkey baster is good for this or a piece of airline running a siphon into a bucket.
Because of this maintenance, a weekly maintenance routine is required on your aquarium to keep it clean. This could be a lot for a beginner!
If you are starting out you will be wanting to watch the wallet and setting up an aquarium can be a big expense. Correctly sizing your HOB is important.
The best way is to first purchase the best skimmer recommended for your aquarium. If it is a HOB protein skimmer, install it and then see how much room you have left along the back wall of your aquarium.
My advice here would be to rather than by the biggest in the range, buy two filters that will fit side by side. Buying two will almost certainly give you more area for filter media which will greatly improve your aquarium.
For Example: 50 Gallon Aquarium 36″ Long x 18″ Wide
Reef Octopus Classic 1000 HOB Protein Skimmer (View it Here at Marine Depot)
Footprint = 8″ x 3.5″
This will leave us with 28″ to fit HOB filters.
Running 2 of any of the filters below will fit the space left over and give you optimal media capacity.
2x MarineLand Penguin 200 BIO-Wheel Power Filter
2x Aqueon QuietFlow LED PRO Aquarium Power Filters
2x Hagen Aqua Clear 70 HOB Power Filter
2x Fluval C4 Power Filter
(All links to Amazon.com for further info)
Briefly mentioned earlier, any splashing from saltwater will leave salt deposits as the drip dries. The water cascading down from HOB filters will splash into the water surface when returning back to the aquarium.
Salt creep must be monitored and cleaned off regularly to not only keep it from affecting other equipment, but prevent it from leaking out of the filter.
Salt creep building up on the HOB filter’s spillway can redirect the water over the edges and onto the floor. Not only does this create a mess on the floor, but if you have an Automatic Top-off system fitted to replace your aquarium for evaporation loss, it will top off your aquarium with freshwater and your salinity will drop.
If left unchecked this drop in salinity will be enough to kill your fish and coral!
To really get the most out of your filters there are a few upgrades mentioned earlier and some others that can really improve their operation.
This is a synthetic filter media that is designed to absorb Ammonia, Nitrite and Nitrate compounds. It also has an added benefit of polishing the water similar to what Activated Carbon does.
As the Purigen becomes exhausted it changes its color to dark blue and eventually black. The great benefit to this product is that you can recharge the media by removing it and washing it in a bleach and water solution.
Purigen can be run in a mesh bag in your HOB filter.
Recommended usage is 1ml for every gallon
This is a manufactured mix of Activated Carbon and a ‘Purigen’ type of ion removing compound that helps to remove organic waste and absorb the harmful Ammonia, Nitrate and Nitrate compounds.
It comes in a bag which can be placed in the filter and will have to be disposed of once it is exhausted.
The manufacturer recommends you change this out every 4-6 months providing you have sized the amount of Chemipure correctly. Once your aquarium begins to get cloudy, it’s time to change the media.
You can now also get Chemipure Elite which adds a Ferric Oxide material to the media to help reduce Phosphates and Silicates at the same time, but only lasts 4 months.
Recommended usage is 1 unit for every 5 – 40 gallons
Carbon or Activated Carbon are sticks or granules made from high quality, high porosity Bituminous Coal.
The main purpose of Activated Carbon is to absorb organic pollutants and heavy metals from the water.
The other benefit of using Carbon is that it will polish your water and make it sparkle. If you look at your tank and you see the water has a yellow tinge to it, then its time to replace the Carbon.
This type of filter media is designed to house beneficial bacteria. They are created just like the sponges to provide the most amount of surface area per piece to get as much bacteria growing as possible.
The MarinePure Gems are specifically designed to be small in size to allow them to fit in the small media areas of HOB filters and All-IN-One Aquariums.
Media Baskets are a nice little invention pioneered by SteveT over at InTank.
The media baskets are designed to replace standard media trays that come with many filters, but allow for better water flow through the media and for easy cleaning.
His media baskets for HOB filters allow for just the filter floss to be easily replaced without having to remove the whole media basket.
For Media Baskets to fit many different filters and aquariums see here:
InTank Media Baskets at Marine Depot
Alternative Filter Methods
If you are in the planning stages of your first aquarium, your next aquarium or are just wondering about HOB filters then here are some other aquarium options to think about.
The main downsides to using Hang-On-Back equipment, not just filters are:
- All the equipment is visible both in the aquarium and above the aquarium taking away the beauty of what’s inside it.
- You are limited to the range of products you can find as Hang-On-Back
- You are limited to the amount of equipment you can place in the space provided
- Maintenance can be laborious and regular with HOB equipment
Luckily there are some other options you may want to consider:
AIO Aquariums stand for All-In-One Aquariums and they are in essence an aquarium with a filter compartment manufactured into the back of the tank. This allows you more space for equipment and it can keep everything out of sight.
There are some awesome AIO aquariums from the small 13.5 Gall Fluval Sea Evo all the way through to Innovative Marine’s Nuvo 80 Gallon with every size in between.
An aquarium with a sump is probably the most common setup you will find in saltwater. The aquarium comes with an overflow system with drilled holes that allow the water to drain into a sump below and then returned to the aquarium via a pump.
Having a sump allows you lots of space for equipment and it keeps EVERYTHING hidden out of sight. They give better access for maintenance and you will be surprised at what you can fit into the aquarium cabinet!
You can buy aquarium systems complete with the aquarium, sump and stand or you can buy all the parts individually to suit your needs.
For more information on setting up an AIO or a Sump-Based system please take a look at my Setup-Guide below. I have a range of all different tank sizes, recommended equipment and costs to help you decide your next aquarium!
HOB filters are a great way to give started in saltwater aquariums and providing you size the filter correctly, fit it with a few of the upgrades and keep it maintained you will be on your way to a beautiful reef aquarium!
With time, you will probably find that it may become a lot of work and the decision to upgrade will start to rattle around in your brain. This is where most aquarists upgrade to an AIO or sump-system aquarium and then never look back.
If you found this article helpful please have a look at some of our other articles that go into greater detail on some of the items mentioned here.
- What Is A Refugium?
- What Is Live Rock?
- What Is An Aquarium Auto Top Off?
- Types of Aquarium Filter Media & What They Do
- What Is A Protein Skimmer And Do I Need One?
- What Is An All-In-One (AIO) Aquarium?
- Everything You Need To Know About Aquarium Sumps