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

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 the best one will be a daunting task if you don’t know how to find a suitable one.

We have compiled the best overflow box reviews and a buying guide so that you can make an informed decision. This guide will explain everything you should know when buying an overflow box and install 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


  • Built with quality in mind.
  • Extremely simple to install.
  • Best suited for 10 to 20-gallon fish tanks.
  • The dual drain construction keep the operation going even if one of them gets clogged.
  • Doesn’t require you to drill any holes at all.


  • 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 ¾-inch bulkhead and ¾-inch PVC that you can directly connect to the bulkhead. The box is around 7.5-inch tall, 4-inch wide, and 2.5-inch 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 last for a long time if you have installed it 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


  • Made of high quality and durable fiber.
  • Effortless to install.
  • Suitable for large fish tanks.
  • This overflow box doesn’t need much maintenance.
  • Includes various installation accessories.


  • 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 also made of fiber materials, and it is pretty rugged.

You can expect a reliable performance plus, 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 as well. 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 package detail including a hole saw, wing nuts, nylon screw along with red PVC pipe to ensure that you can conveniently install it on our aquarium. It measures to be 12-inch x 3-inch x 6-inch in size. Plus, 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 works well with fresh and saltwater. It is made of fiber materials and works well when flowing water at high speeds.

3. Eshopps AEO11015 Overflow Box


  • Best suited for tanks up to 200 gallons.
  • Pretty simple to install.
  • Does not require much maintenance.
  • Double drain design continues to work even if one gets clogged.
  • Made of quality fiber materials.


  • 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 different fish tanks that are up to 200 gallons in capacity. Therefore, if you look for an even bigger overflow box than the Eclipse by Eshopps, go for this model.

It has that trademark simple to install design that comes from Eshopps. 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 well.

As this overflow box for the saltwater tank 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 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 and won’t take much maintenance either.

4. Eshopps PF300 Overflow Box


  • Effortless installation.
  • Made of fiberglass and has a robust construction.
  • Comes with a flow rate of 300 gallons per hour.
  • An excellent choice for tanks up to 75 gallons in water capacity.
  • The package includes everything you need for installation.


  • It is a bit noisier as compared to 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 developed this brief buying guide to guide you in making the right decision and choosing the best overflow box.


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 either. But this setup is pretty expensive, and the cost might seem even more than drilling 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 ten like if you have a 30-gal tank, then multiply it with ten 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 a better option if you 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 a 1-inch air, 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. It 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 if one of the holes gets clogged. This high-quality overflow box will work very well for both saltwater 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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