Whether you have a saltwater or freshwater tank, you will need the best overflow box for cleaner installation and maintenance.

An aquarium overflow box is your entry point where you install a sump. It can filter the scum front of the water surface automatically and will keep your aquarium clean all the time.

There are different types of overflow boxes available on the market. So, choosing one for your aquarium will be a daunting task if you don’t know what you should be looking for.

To help you make a more informed decision, we have compiled the best overflow box reviews and made a buying guide. This will explain everything you should know when buying an overflow box and installing it on your aquariums.

Keep reading to find out!

Comparison Chart

Products Flow rate Suitable for Materials
Eshopps AEO10100

200 gallons per hour Up to 20 gallons tanks Fiber, nylon, and PVC
Eshopps Eclipse

1000 gallons per hour Up to 150 gallons Fiber, nylon, and PVC
Eshopps AEO11015

1250 gallons per hour Up to 200 gallons Fiber, nylon, and PVC
Eshopps PF300 300 gallons per hour Up to 75 gallons Fiber, nylon, and PVC

Best Overflow Boxes Reviewed

1. Eshopps AEO10100 Overflow Box


  • This was built with quality in mind.
  • It is extremely simple to install.
  • It is best suited for 10- to 20-gallon fish tanks.
  • Its dual drain construction keeps the operation going even if one of them gets clogged.
  • It doesn’t require you to drill any holes at all.


  • It is not a great choice for larger tanks.


This hang on overflow box is suitable for all aquariums and fish tanks of up to 20 gallons in capacity. The box is simple to install, and you won’t have to go through a lot to get it all done. It comes with a dual drain design, and it will be beneficial if one of them gets clogged for some reason.

So, your system will continue to work as well as ever. It features a 0.75-inch bulkhead and 0.75-inch PVC that you can directly connect to the bulkhead. The box is around 7.5 inches tall, 4 inches wide, and 2.5 inches deep, and the best part is that you won’t have to drill any holes with this overflow box. It means the installation is simple and straightforward.

It is a good-quality overflow box made of durable materials and will surely last for a long time if installed properly. Another exceptional feature of this overflow box is that it is very quiet in operation.


It is the best aquarium overflow box for 20-gallon fish tanks. It is made of robot materials and is simple to install.

2. Eshopps Eclipse Overflow Box


  • This overflow box is made of high-quality and durable fiber.
  • It doesn’t require much effort to install.
  • It is suitable for large fish tanks.
  • This overflow box doesn’t need much maintenance.
  • The kit includes various installation accessories.


  • It is not made for smaller tanks.


If you’re looking for an overflow box designed for larger fish tanks and aquariums, you need to go for this one by Eshopps. This overflow box is made of fiber materials and it is pretty rugged.

You can expect reliable performance from this box. Additionally, the company has fine-tuned it for noise reduction during operation. It has a minimalistic design, so it is not going to take much space either. But you won’t have to compromise on the flow. This overflow box can be transported with ease. It features a plug-and-play design, so installation is not going to be an issue at all.

Your purchase will include a hole saw, wing nuts, nylon screw along with red PVC pipe to ensure that you can conveniently install it on our aquarium. It is 12 inches x 3 inches x 6 inches in size. In addition, it has a solid construction that will continue to work for you for a long time.


This is an overflow box that is great for larger aquarium tanks and is compatible with freshwater and saltwater. It is made of fiber materials and works well even with high-speed flowing water.

3. Eshopps AEO11015 Overflow Box


  • This box is best suited for tanks up to 200 gallons.
  • It is pretty simple to install.
  • It does not require much maintenance.
  • The double drain design continues to work even if one gets clogged.
  • It is made of quality fiber materials.


  • Unfortunately, it is not the best choice for smaller aquariums.


This overflow box for aquarium tanks comes with a flow rate of up to 1250 gallons per hour, and it is an ideal choice for fish tanks that are up to 200 gallons in capacity. Therefore, if you are looking for an even bigger overflow box than the Eclipse by Eshopps, go for this model.

It has that trademark simple-to-install design that Eshopps products are known for. This design also features a dual drain construction that ensures the flow continues even if one of the holes gets clogged for some reason. The unit is convenient to install, and you don’t have to do much besides finding the right sized tank. You also won’t have to drill any holes in the tank.

As this overflow box is made of fiber material, it will not deteriorate for any reason and will continue to perform for a long time. You also won’t have to do much maintenance work to keep it in shape.


This saltwater overflow box is an excellent choice for fish tanks that are up to 200 gallons in capacity. This tank overflow box has an easy installation process and won’t need much maintenance either.

4. Eshopps PF300 Overflow Box


  • The installation doesn’t require much effort.
  • It is made of fiberglass and has a robust construction.
  • It comes with a flow rate of 300 gallons per hour.
  • It is an excellent choice for tanks with up to 75 gallons in water capacity.
  • The package includes everything you need for installation.


  • It is a bit noisier compared with other Eshopps overflow boxes.


This tank overflow box is a suitable choice for fish tanks up to 75 gallons in capacity. As it is from Eshopps, the box has a plug-and-play design that doesn’t require much effort to install.

This overflow box for the aquarium is made of fiberglass. It will stand the test of time and won’t need much cleaning and maintenance from you. Additionally, this unit comes with a flow rate of up to 300 gallons per hour, suitable for mid-sized fish tanks.

Another feature that we found very useful is that it works well for both freshwater and saltwater tanks. So no matter what your setup is, you will find this overflow box very handy. But this fish tank overflow box is slightly noisy, especially if you compare it with other units mentioned here.


It is a slightly noisy unit but not loud enough to consider as a dealbreaker. You will love using this overflow box to work for any fish tank up to 75 gallons in capacity.

Buying Guide

To make sure that you pick the right product, we have created this comprehensive buying guide. This will help you in making the right decision and choosing the overflow box that best suits your needs.


1. Internal hand-on designed overflow boxes

The internal overflow boxes are straightforward and effortless to install, but they also have the most significant risk when it comes to failure in your fish tank. This failure usually is regarding the loss siphon caused by the failing tubes, power outage, or faulty pump.

These boxes are most affordable and are great if you don’t want to drill any holes in your tank. You can mitigate these issues only by making a larger sump.

2. International inbuilt overflow boxes

The overflow box for saltwater tank has an integrated design. They are usually great with one hole, but these boxes are not very silent in operation. This setup is pretty expensive. It will cost more compared to when you choose to drill holes in your tank.

3. External overflow boxes

It is the best option out of the three for features because it is rich in this department. You can do any setup and configuration in this design, and some of them also come with slim overflow designs.

It leaves an almost negligible footprint inside your tank. But you can’t have a flush aquarium, and the box will stick out. Plus, you will also have to drill your tank, and that can be troubling in the long run and adds to the overall cost for maintenance.


These overflow boxes have self-regulating designs, and they won’t drain more than what enters them. Hence, you need to be careful about choosing the right overflow box that goes well with the return pipe.

It would be a good idea to purchase the return pipe first and then go for an overflow box to make sure that you won’t have to deal with any issues later on. The package needs to have a higher flow rating than the pump. If you have the box already with you, choose the return pump carefully and ensure the flow rate is lower than the box’s flow rate.

You can also calculate the overflow box’s adequate size by considering the size of your fish tank. Just multiply it by 10 like if you have a 30-gallon tank, then multiply it with 10 to get 300 in terms of gallons per hour. Now you will need a box that has a flow rate bigger than 300 gallons per hour.

Preparing for an Installation

1. Hang-on overflow box

It will be better to go for a complete frill-free option if you have no prior experience with it. You will need a U-Tuber return to get the water into the tank in a proper manner.

It will support 1-inch air and a 0.75-inch tubing and is effortless to install. As its color is black, it is going to work well if you have a black background.

2. External overflow box

For an external overflow box, you will need to drill some holes in your tank. For that, you will need hole saws, a drilling template, a drill stand, a corded drill, and a plumber’s putty. You will have to make sure that the tank is not made of tempered glass.

Here is everything you need to know when looking to drill a hole in your fish tank. If you follow the instructions carefully, you will make those clean holes and install your external flow box in your tank pretty conveniently.


There you have it. The best overflow box that you should consider installing on your aquarium tank is the Eshopps AEO10100 Overflow Box. This unit is made of fiber materials and is extremely easy to install. It’s a great choice for any fish tank that can hold more than 20 gallons of water in it.

It also features dual drain construction to keep the flow going even if one of the holes gets clogged. This high-quality overflow box will work very well for both saltwater tanks and freshwater tanks. You don’t have to maintain the setup a lot, and it will continue to work for a long time to come.


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