4 Top Ranked Super Sleek Hang-on Overflow Boxes

Most of the reef tank and aquarium lovers completely understand the importance of an overflow box. The prime advantage of utilizing an overflow box is that it makes sure that your display tank consistently maintains the optimal level of water all time.

To replenish evaporated water in an effective manner, overflow tank properly pumps in the optimal level of water quickly after sensing the low level of water in a tank. To remove the impurities, it also pumps aquarium water through a filter. Want to learn about the best auto feeders ?

Categories of Overflow Boxes

Purchasing a Hang-On Overflow Box

Other main factors that you should consider are:

  • Is it quick and easy to install?
  • Is there any chance of quick clogging?
  • How is the overall quality?
  • How much noise does it create?

The main thing is that it is all up to your understanding and choice to get the wet/dry filters, sump, refugium that you want for your tank.

Best 4 Super Sleek Hang-on Overflow Boxes

1. Eshopps Overflow Box


  • It usually works in the proper manner as it claims, according to most of the buyers.
  • The installation process is highly simple and quick for almost all aquarium veterans.
  • It does not produce much sound as compared to other models, although it is not entirely silent.


  • If you are new to the use of an aquarium, then definitely installing this will not be easy for you. Usually, it does not come with any setup instruction manual which should be included in it.
  • Many people also say that it, in reality, has an 800 gph flow rate.
  • Moreover, you might have to face some overflow problems during the power outage.

Mainly, here we are discussing the PF-800 overflow box, which is considered as the optimal box for 75 to 125-gallon aquariums as recommended by Eshopps. You can also have a look at the best under tank heater.

The dimensions of this box are 8 by 3 by 10 inches that simply means that there is the need of 3 inches of space between the tank and the wall.

This basically contains the U-tube siphon, pre-filter box, cylinder foams, and other essential items such as wing nuts and nylon screw.

2. Aqueon Hang-On Overflow Box


  • As it offers the capacity of 2200 gph, it is perfect and quite effective to handle return pump flow rates.
  • The setup is not much complicated, which is true for any HOB option.
  • It’s also very good and effective in maintaining siphon.


  • There are few people who do not trust and like the quality of Aqueon. So it is recommended to check first for leaks over the sink before buying. Some other people also complained that after the use of a few years, it falls apart.

This overflow box is basically for 125-gallon tank but the company also offers a 400-gallon version of this box.

It is very difficult to do proper and deep research on this as the Aqueon doesn’t provide any detailed description of its features even on its own official website.  The only information that it gives is its dimensions which are 8.3" x 6.3" x 11.5".

Moreover, its design does seem to offer an easy and quick setup as it basically made with a dual drain design. The best thing about this box is that if the drains get clogged, it can handle quite a bit of water.

3. KollerCraft TOM RP3 Overflow Box


  • It contains the proper hoses and clamps.
  • It is very easy to set up this overflow box and installation can be done by the beginner tank owners as well.


  • There are also some people who have complained that they do not get the clamps or hoses that should be given with the purchase.
  • Many people also believe that it’s quite overrated in terms of its overall flow rate capacity.

The dimensions of this overflow box are 8 by 7.5 by 6.5 inches (LHW). It is perfect to use for tank frames of maximum 1.75 inches thickness. It’s also rated for 800 gph pumps.

Moreover, its gravity system primes without any external efforts and specifically in an automatic way. To prevent excessive overflow of water, it also contains an anti-siphon feature.

4. CPR CS90 Overflow Box


  • It is absolutely simple to clean and use.
  • It is also very effective in dealing with a power outage.
  • It does not produce much sound.


  • To use this in a proper manner, your return pump should have a flow rate lower than 600gph.
  • To completely maximize its efficiency level, you need to use it with the Aqua Lifter.

This model of overflow box offers 600gph overflow rate and rated for 125-gallon tanks as well. It also provides a quite simple way to adjust the level of water and to prevent the growth of algae; it also contains a black top.

My Pick

In my opinion, all these different types of overflow box work in a proper and effective manner. But if we look for optimal consistency level, then CPR CS90 works great but only if you use the Aqua Lifter pump to with it.

Moreover, it has also received the best reviews from many people. There is hardly any case where you hear about the failure and missing pieces of this box.

Feel free to share your thoughts, submit your questions, and give your valuable recommendations to us.


[Revised and Updated for July, 2019]
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Written by Debra Hutchinson, founder of FishXperts

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