How To Set Up A Coral Frag Tank

In this article, I will explain the proper methods for setting up a frag tank.

Setting up a frag tank is just one of the many ways to expand in the hobby and keep things interesting.

Frag tanks can be very rewarding and it’s a great way to build out your coral collection to sell or trade with other hobbyists.

It doesn’t take long for certain corals to grow and before you know it, your main tank will fill up as your corals grow into colonies.

It’s a good idea to consider fragging them and move the smaller frags into a separate frag tank.

Before you set up a frag tank, it’s important to understand the steps and equipment required ahead of time which can save you time, money, and effort.

What is a Frag Tank?

A frag tank is a separate working tank where corals are to be placed where they will heal and grow in an ideal and clean environment.

These corals usually come from your display tank where they are fragged and then placed into a frag tank.


Image: Marine Depot – Click for more Info about frag tanks

What equipment is needed to set up a frag tank?

When choosing the aquarium to be used for the frag tank, there are a few factors to keep in mind. Although you can use any tank size and dimensions, it’s best to choose a tank that will allow a large enough area for the frags to be placed without touching each other.

It will need to be long and wide enough for frag racks, egg crate, etc. The maximum surface area you can have will be better.

Most people will also choose a tank size that is shorter than others. A shallow tank will not only be easier to maintain but if you have frags that are more light-demanding, a shallow tank is beneficial for them.

Also, consider using a rimless tank as it is easier to access, install, and remove egg crate if you are using them.

Other than the tank itself, there are a few more things that you will need.

Check out one of my favorite frag tanks here.


Depending on the types of coral frags you are keeping, plan your lighting accordingly to meet their demands. Where most frag tanks are shallow, you won’t need a high end or expensive lighting system. You can use something like the Kessil A80 or USA Orbit Marine LED. 

current usa orbit led

Water movement

Certain corals will have different requirements for water flow. Proper water movement is crucial for their growth and overall health. You can use a basic powerhead for a frag tank that is affordable and will provide the right amount of flow for your corals.


Depending on the tank you are using, you will have the option of an all in one tank or sump system. All in one tanks are great as you will have a rear chamber for all your filtration and it is a self-contained system that is easy to maintain. If these are not an option for you, then a basic hang on the back filter will work as well.


You will need a heater that will maintain the proper water temperature inside the frag tank. Make sure that the wattage of the heater is sufficient for your tank size. Aim to choose a heater that is 3-5 watts power per gallon of water. I recommend the Cobalt Neo-Therm as it’s slim design works great for frag tanks.

Frag racks

Frag racks are used to hold your frags once mounted on plugs or discs. There are many different sizes and types to choose from.


Live sand and rock are not normally kept inside a frag tank. If you are using a sump system, you can add live rock there if you like. You want to keep the frag tank as clean as possible which will improve water quality. I prefer to keep a frag tank with minimal equipment. Using a bare bottom tank with frag racks, egg crate to hold the frags in sections is all you need to aquascape the tank.


Marine Depot Aquarium Supplies

Is a protein skimmer needed for a frag tank?

A protein skimmer is not necessary for a frag tank. 

Without fish in your frag tank, your system will have lower organic waste than your main tank.

Although it will help keep your water clean, it is an optional piece of equipment for a frag tank.

Do you need to cycle a frag tank?

Once you have the required tank and equipment, you can fill it with salt water and start the cycle.

Yes, it is important to complete the tank cycle prior to putting corals in the tank.

Establishing the nitrogen cycle will ensure that your corals are going into a healthy environment.


What Is The Easiest Way To Cycle A Frag Tank?

One of the best ways to cycle your tank is by using established live rock. This is the most common and effective method.

Live rock contains nitrifying bacteria to ensure any ammonia present will get broken down into nitrate.

You can also use nitrifying bacteria in a bottle and introduce it into the tank. This will help populate dry rock in your tank.

Microbacter7 is a great product and many people use it for cycling their tank.

Traditional cycling methods can also be used. It is not the most effective and it takes longer but it’s a common way to ensure a proper cycle.

This method requires the introduction of ammonia to the system. This can be in the form of a frozen shrimp left to rot in the water, or directly dosing ammonia.

This can take up to 4-8 weeks to complete.

Can I use used water for cycling the tank?

Using water from another tank will not cycle your frag tank. The bacteria needed to cycle the tank is not present in the water column like it is in live rock or bacteria products.

You can use the water from another tank if you have extra but it will not cycle the tank.


Read: Best corals for fragging – easy for beginners

How long should I wait before adding corals?

Once your tank is cycled you can start adding corals. You will know the tank is cycled when the ammonia and nitrite levels are 0. This can take 4-8 weeks.

If you started your frag tank using live rock, you can speed up the process.


Tips For Keeping a Frag Tank Algae Free

There are a few ways to prevent algae from forming in your frag tank. The best way is to use a bare bottom tank with plenty of water flow. Strong water flow will prevent detritus from settling on the bottom of the tank and other surfaces. Detritus when settled will cause an increase in phosphates and the algae that follow.

Also plan to keep a solid clean-up crew in your frag tank. A good crew of cleaners will do a great job in keeping your tank algae free. Turbo and Astrea snails, hermit crabs, urchins, shrimp, are all good choices.

Prevent unwanted phosphates from entering your tank. 2 common sources include tap water and uneaten foods. Always use RODI water for your frag tanks and perform routine maintenance including water changes to remove any uneaten foods in the tank.


Setting up a frag tank can be a very simple process and you don’t need high end or expensive equipment. You can even plumb a frag tank into your existing display tank which would eliminate the need for certain equipment like heaters and filters. Frag tanks are a very unique part of the hobby and once you set up your first frag tank, you will be hooked.