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5 Best Hang-On-Back Overflow Boxes in 2022 – Reviews & Top Picks

Lindsey Stanton Profile Picture

By Lindsey Stanton

5 gallon fish tank

Overflow boxes are some pretty convenient aquarium accessories. Their biggest benefit is that you can use them to house more and bigger equipment that you want hidden from display. Pumps, sumps, and filters of all kinds don’t look very nice, which is where the overflow box comes in.

Today, we want to take a look at some of the best hang-on-back overflow boxes out there (this is our top pick), to help you find the one that works best for you.

starfish divider ahA Quick Comparison of Our Favorites in 2022

Rating Image Product Details
Best Overall
Winner
Eshopps Pf-800 Overflow Box Eshopps Pf-800 Overflow Box
  • Durable
  • Space friendly
  • Best Value
    Second place
    Aqueon Hang-On Overflow Box Aqueon Hang-On Overflow Box
  • Very easy to set up
  • Dual drains to prevent clogging
  • Premium Choice
    Third place
    CPR CS90 Overflow Box CPR CS90 Overflow Box
  • Adjustable water level
  • High flow rate
  • OF 600 Overflow Box OF 600 Overflow Box
  • Fairly quiet
  • Good for aquariums up to 125 gallons
  • Tunze Hang on Back Aquarium Overflow Box Tunze Hang on Back Aquarium Overflow Box
  • Self-priming
  • Restarts automatically after shutting off
  • The 5 Best Hang On Back Overflow Boxes

    Let us start by taking a look at our pick that we personally feel is the top contender. It’s got quite a few nifty features that you might really appreciate.

    1. Eshopps Pf-800 Overflow Box

    Eshopps Pf-800 Overflow Box

    Check Price on Chewy

    Features

    The Eshopps Pf-800 can be used for any aquarium up to 400 gallons in size. What is really neat about this thing is that you can use it for small aquariums such as 30-gallon tanks, or for anything up to 400 gallons as well.

    Something that comes in quite handy here is that it has dual drains that lead down to the sump or back into the aquarium if you choose. In case one gets clogged, there is another one as a backup.

    It helps to stop the Pf-800 Overflow Box itself from overflowing. It’s a very simple to install hang on back overflow box. More or less, just hang it over the back of your aquarium, put the siphon in the tank, and connect the drain tube to the sump.

    Furthermore, the Pf-800 comes with cylinder foam pads over the drainpipe, which is pretty convenient as well. This more or less acts as a flow regulator, plus it helps filter solid debris out of the water as well. In other words, it cleans the water and makes sure that the drain pipe does not get clogged.

    This overflow box is very durable and well-built. Only the highest quality materials were used here. At the same time, it is actually pretty lightweight and not all that bulky, which helps with setup and spatial requirements. One complaint is that it is a bit loud, but it does get the job done.

    Pros
    • Durable
    • Space friendly
    • Does not clog easily
    • Has a foam filtration pad
    • Very easy to set up
    • Works for small and large aquariums
    Cons
    • Very loud
    • Fitting the hoses can be a little difficult

    2. Aqueon Hang-On Overflow Box

    Aqueon Hang-On Overflow Box

    This is another really simple and effective hang-on-back overflow box. For one, it is made to be quite durable. No, the materials used are not of the highest quality out there, but they should last for a good while, assuming it’s properly looked after.

    The fact that it is so easy to set up is definitely an advantage. All you have to do is connect the tubing or hoses to your sump, hang the Aqueon Hang-On Overflow Box on the aquarium, and you are good to go.

    The Aqueon HOB Overflow Box features dual drains, which are always useful. You don’t want your box overflowing, as this will cause problems. In case one drain clogs, the other one will pick up the slack. The foam pad included here is pretty useful as well, as it filters out solid debris, thus cleaning the water and helping to prevent clogging.

    This thing can be used for any aquarium up to 125 gallons in size. However, there is an option of this model that can be used for aquariums up to 400 gallons.

    One thing that needs to be said here is that this particular overflow box is definitely not very good looking. Yes, it is quite durable, effective, and it gets the job done, but it is not stylish, nor is it quiet.

    Pros
    • Good for tanks up to 125 gallons
    • Quite durable
    • Dual drains to prevent clogging
    • Foam pad for some debris filtration
    • Very easy to set up
    Cons
    • Not good-looking
    • Loud

    3. CPR CS90 Overflow Box

    CPR CS90 Overflow Box

    This is another nice overflow box to consider, and it is one that is rated for aquariums up to 100 gallons. If you have a decent home aquarium, this should be more than ideal for you. What is pretty cool about the CPR CS90 Overflow Box is that it features an adjustable water level, so you can control how much water is being siphoned from the aquarium to the sump. It’s an easy way to adjust the water level in the tank as well.

    The bulkhead included is perhaps the best way to drain water from an aquarium to a sump or a filtration unit. It is quite efficient and it works well. The black top of the CPR CS90 is also designed to help reduce algae blooms and buildups. The CPR CS90 Box does have a flow rate of about 600 gallons per hour, which is fairly impressive.

    This box is easy to install, as most hang-on-back overflow boxes tend to be. This particular HOB overflow box also comes with dual drains, which, once again, is great in case one gets clogged. The drains both come with foam filter pads equipped to help clean the water of solid debris and to prevent clogging as well. This is a fairly space-efficient model to go with, yet another bonus.

    Pros
    • Space friendly
    • Adjustable water level
    • Dual drains to prevent clogging
    • Dual foam filters for debris removal
    • High flow rate
    • Rated for aquariums up to 125 gallons
    Cons
    • Not the most durable
    • A bit loud

    4. OF 600 Overflow Box

    OF 600 Overflow Box

    This is a great continuous overflow box to consider, one that works without the U-tubes. The OF 600 Overflow Box has a flow rate of 600 gallons per hour and is rated for aquariums up to 125 gallons in size. This should be more than enough for most home aquariums. One thing to note here, unlike with the other models we have looked at, is the OF 600 does not come with foam filter pads.

    The OF 600 is very easy to install. Just hang it on the back of your aquarium, connect the hoses to the sump, and you are good to go. It really does not get any easier than that.

    While it is not the most space-friendly design out there, it does get the job done. We personally like that the ID bulkhead that is included here, as it is quite efficient and effective.

    The OF 600 Overflow Box only features a single drain, which is not exactly ideal when it comes to preventing clogs. However, what is really cool is that the OF 600 Overflow Box is made out of solid acrylic and other very rugged materials. A lack of durability is definitely not an issue when it comes to this particular hang-on-back overflow box.

    Pros
    • Very durable
    • Good for aquariums up to 125 gallons
    • High flow rate
    • Fairly quiet
    • Very easy to set up
    Cons
    • No foam filtration pads
    • May clog on occasion

    5. Tunze Hang on Back Aquarium Overflow Box

    Tunze Hang on Back Aquarium Overflow Box

    The Tunze Hang on Back Aquarium Overflow Box comes with a flow rate of 320 gallons per hour. It is a very efficient model of hang-on-back overflow box to go with. While it is actually not all that small, the box itself is not designed for larger aquariums. It’s a good option for any aquarium up to 100 gallons.

    On a side note, if you get an additional U-pipe, you can use this box and produce over 400 gallons of flow per hour.

    The Tunze Hang on Back Aquarium Overflow Box is easy to set up, as it can just be hung on the back of your aquarium and connected to your sump. It is a self-priming model, plus if it shuts off, it will automatically restart without any issue.

    The Tunze Hang on Back Aquarium Overflow Box is built to be very quiet. Also, this particular model is built to be extremely durable as well. It should last for quite a few years.

    Pros
    • Durable
    • Quiet
    • Can be upgraded with extra parts
    • Self-priming
    • Restarts automatically after shutting off
    • Good for aquariums up to 100 gallons
    • Efficient
    Cons
    • Cannot see the interior – black walls
    • Not too space-friendly
    • Big and bulky

    starfish divider ahBuyers Guide: How To Choose The Right Overflow Box

    Choosing the right overflow box for your aquarium is not that hard at all. There are only a few considerations to keep in mind, so let’s talk about those right now.

    Internal or External

    We’re going to talk about the differences between internal and external overflows in more detail below. However, the main thing to keep in mind here is that external overflows don’t take up much space inside the tank. Plus, they tend to be much easier to install than internal overflows.

    With that being said, they are usually more expensive and a little less versatile than internal overflows.

    The Size

    The most important consideration to keep in mind when looking at an external overflow box is the size. Now, you do need to keep the spatial requirements in mind, especially in terms of the clearance behind the tank. However, this is not actually what we are talking about here.

    You need to get the right size of external overflow box according to the return pump from your sump. For instance, if your return pump is rated at 250 gallons per hour, you will want the overflow box to be rated for at least 300 gallons per hour, if not 350 gallons per hour.

    The Drains & Filter

    A convenient thing to have when it comes to overflow boxes is dual drainage pipes. Yes, single pipes work just fine in most cases, but if the single pipe gets clogged, the box will overflow, which is bad. Having an overflow box with dual drains means that if one gets clogged, the other can pick up the slack.

    At the same time, having foam filters over the drain pipes is ideal, as they help to stop solid debris from flowing into the sump and prevent clogging.

    starfish divider ahConclusion

    As you can see, hang-on-back overflow boxes are very convenient. Some people might prefer the interior overflow boxes, but having to drill holes in your aquarium is just not a good idea. We would, of course, recommend our own number one pick, but at the end of the day, all of the models we have looked at here could very well take the spot for the best hang-on-back overflow box.


    Featured image: Ja Crispy, Shutterstock

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