Are Water Changes Necessary In Reef Tanks?

Water changes are something that are often avoided with saltwater hobbyists. Let’s face it, they are not the most exciting thing in the world to do.

Maintaining clean and healthy water is not only required for maintaining the aesthetics of an aquarium but is also a fundamental requirement for maintaining the health of the fish in it. 

are water changes necessary in reef tanks

Sometimes water changes can sound simple and easy to do but if you have a saltwater reef tank there are many factors to consider and it can lead to a time consuming and tedious task.

To answer the question are water changes necessary in reef tanks? The answer is yes.

It is very important to perform water changes on a regular basis.

In order to keep a successful reef tank you must keep up with proper husbandry and maintenance. This includes performing water changes.

I follow a specific water change schedule on my tanks. There are many reasons why you should perform regular water changes on your reef tank.


water change schedule



Not only does a water change help keep the aquarium water crystal clear, but it ensures the livestock in the tank remains healthy. It will actually help keep the whole environment clean, healthy, and in balance.

There are many saltwater hobbyists that don’t perform water changes on their tanks. Just do a search on Youtube and you will find many people showing their saltwater tanks and claim that they don’t do water changes.

It’s a proven fact that there are huge benefits to doing water changes. Some people will argue that you can keep a successful reef tank without doing water changes. I’m not one of them. 


water change for reef tanks


With all the high-tech equipment available in the Hobby today, some people will rely on certain filters and media to reduce the frequency of water changes. The development of many chemical filter media and other efficient filtration systems has reduced the need for water changes that are often laborious and time-consuming.

This filtration extends the quality of the water, and slows down any building up of harmful chemicals, but does not in any way completely reduce the effects of the decline in water quality.

For example, using a sump system on your saltwater reef tank can greatly improve the overall health of your tank. But doesn’t remove the need for making water changes.

You can read more on sumps for saltwater tanks here. 

Water quality in an aquarium is affected by the addition of food and supplements and the natural metabolic processes of the fish that allows various chemicals to be added to the aquarium. While these chemicals get added, some can also be removed through filtration systems.

It is only when the addition and removal of the chemicals are in equilibrium that the water quality in an aquarium, freshwater or saltwater, can be considered good for the fish.


More reasons why water changes are necessary


  • Water changes for saltwater aquariums restore the balance in this closed system by the physical removal of harmful chemicals by diluting them and helping to replenish the vital elements that the water needs. It is always good practice to schedule water changes.


  • It helps to reduce the presence of nitrogenous pollutants, like, ammonia, nitrate, and nitrites. The process of biological filtration converts ammonia to nitrite and then nitrate, and most filtration systems in aquariums are not able to process nitrates. This is the reason why nitrate accumulation is common in aquariums.


Saltwater nitrogen cycle


  • The food and metabolic activity in the fish produce organic waste that decays and affects the quality of the water and its aesthetics. Their decomposition leads to a release of nitrogenous products that cloud the water and affect its quality.


  • Acidic environments can get created, leading to the need for water changes that help to maintain the required pH that is very important for saltwater aquariums. 


  • The high level of nitrates puts the fish under chronic stress, though fish have a tolerance for nitrate. This results in their susceptibility to diseases that lead to their poor growth.


  • Water changes are also helpful in illuminating cloudy aquarium water. If you notice A strong smell or odour coming from the water, a water change will definitely help illuminate this. If you are looking to show off your tank to family or friends a great way to have your tank looking pristine is to perform a water change beforehand.


  • Another benefit of performing regular water changes will replace necessary trace elements for your corals. A good quality salt mix will contain all the necessary elements required to keep corals healthy. Of course you may need to does your tank depending on the amount of livestock you have as not every tank is the same. It’s important to test your water on a regular basis to ensure your tanks needs are being met. Important trace element levels like calcium magnesium and alkalinity must be kept at the proper levels at all times In order for corals to thrive.


There are benefits to performing several small water changes instead of one large water change. Some people say you need to change 25 percent of the water at least once a month. However, if you have larger fish or an aquarium that is heavily stocked, you should change between 15 and 20 percent of the water every week.

This will prevent large water parameter swings and help keep things consistent.

 My advice is to always check your water levels with a proper test kit and do water changes when needed. There is no right or wrong amount to do. Just do them as required by your tank. Every tank setup will be different and require different needs.


Marine Depot Aquarium Supplies


Automatic water changing systems


If you are looking for a very cool but lazy way to perform water changes look into an automatic water change system. Yes there is a way to have your water changes done automatically. These systems are definitely convenient and have certain features built-in that will make water changes and maintaining water levels easy. But are they worth the cost?

Well that is something that you need to determine. I recommend checking out the smart AWC touch if an automatic water change system is something you are interested in.




Do water changes help prevent nuisance algae?


Yes, water changes are actually one of the best ways to illuminate and reduce the growth of algae in your tank.



Water changes can affect the fish and corals in the tank and therefore it’s important to only use good quality water. As mentioned in my post Do You Need To Use RODI Water, RODI water is recommended to use for water changes and top-ups in your saltwater aquarium.

The temperature of the changing water needs to be the same as the water inside the aquarium. Ideal temperatures will be those between 76 and 80 degrees Fahrenheit. The salinity of this water must also match the salinity in the tank, which ideally should be maintained at 35ppt. Specific Gravity 1.026.

There are fancy, expensive equipment you can buy to measure salinity. But it’s not necessary. I recommend using a basic refractometer like this. I have been using these for years without issue!

If you decide to buy saltwater at a local fish store instead of making your own, check the salinity in your tank beforehand to make sure they match.

Mixing your own saltwater is not very complicated. Once you get a system in place that works well for you, it becomes easy to do. You will need to purchase aquarium salt in a store or buy it online. Remember that certain salts are better than others if you have a reef tank.

The Red Sea salt mix and Instant Ocean Reef Crystals are great salts to use and are affordable. They contain essential elements that corals need to thrive.

Use large plastic drums for mixing saltwater. Fill this drum with the amount of RODI water you need and add the salt as suggested in the instructions given on your salt container. Use a powerhead or wavemaker to mix the water over a period of time.

Some people will mix saltwater for 24 hours, and other salts will mix much quicker. It depends on the brand you use. Check the salinity of the water with a refractometer and make any adjustments to the salinity by either adding salt or water and remixing. You will also need to check the temperature of the water to match the water in the aquarium.

Installing a heater into the plastic drum set to the temperature of your tank will be easier and less stressful on fish and corals.

  • Pro tip: Never use saltwater for top-ups. Fresh RODI only. Your water will evaporate daily causing salinity to rise. A good way to avoid this is to use an ATO with RODI water only!

Water changes are something that every saltwater hobbyist should be prepared to do. You will read arguments from some saying that they are not necessary and they get away without doing them. Well to each their own I guess.

Water changes, in my opinion, are very important and will help your tank thrive and stay healthy in the long run. Keep your saltwater tanks looking amazing!