Performing a water change is one of the most critical maintenance tasks for keeping a successful saltwater aquarium. During a water change, a portion of the aquarium water is removed and replaced with clean, properly mixed saltwater. Unfortunately, water changes are also tedious, time-consuming, and easy to neglect for those of you first starting out. We are here to help you understand why these water changes are so critical to the health of your aquarium and will provide you with some insight to help streamline the process making it easier to sustain long-term. 

If this is your first time exploring water changes, be sure to check out the previous episode in our Beginner's Guide To Saltwater Aquariums: 5 Ways to Start a Siphon for an Aquarium Water Change - Beginner's Guide Ep: 24

Why Are Water Changes Important?

It has been proven time and time again that hobbyists who maintain a water change schedule will drastically increase their chances of having a successful aquarium past the first 12 months. In other words, performing these water changes just helps you achieve long-term aquarium success. The reasons are pretty clear.

Forces Contact Time With Your Tank

Performing water changes every 7-14 days means you will have intimate time with your tank and its inhabitants on a very regular basis. You will be accustomed to your equipment and the animals your keeping, making it easier to identify problems before they spiral out of control.  

Removes Waste And Harmful Build-up

During a water change, you will clean your sand bed and remove a portion of the dissolved phosphate, nitrate, and even ammonia from the water. You will also be removing suspended detritus/debris, algae, leftover food, fish waste, and any other harmful contaminants that might have found their way into your tank. 

Adds Major, Minor, & Trace Elements

Freshly mixed, clean saltwater has all of the saltwater elements at their natural ratios. This means, when doing a water change you will be rebalancing the water chemistry and replenishing these elements that may have been depleted.  

Prevents Issues From Compounding

By performing regular maintenance, you will be ensuring small problems are not allowed to compound, creating something even worse.  Both waste and nutrient removal as well as stability in terms of water chemistry benefit from the process, both of which are critical to the health of your tank.  If these things are left unchecked and water changes are neglected, you are headed down a path riddled with frustration and failures.

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How Often Should I Change Water?

If you are changing the water once per week, every 7 days, you are doing great and will be giving yourself the highest chance of success.  Once every 14 days, you are on par with most aquarium owners.  Beyond that, you are neglecting the needs of your tank to an extent. 

How Much Water Do I Need To Change?

The general recommendation is 10% - 20% every 7-14 days based on your particular tank's needs.  10% weekly is ideal, but 20% every two weeks will suffice for many tanks.  Smaller more frequent water changes are always going to be more effective than larger, infrequent water changes. If you decide to wait 30 days, you will likely find yourself changing out a much larger volume of water closer to 50%. 

These smaller water changes are just more manageable and easier to perform compared to much larger percentage water changes.  For example, 10% of a 50-gallon tank is only 5 gallons of water, which is easy to mix, manage, and even store at home. 50% of a 50-gallon tank is 25 gallons of water which simply requires more time and effort to manage, let alone much larger containers.  

All that said, be realistic. Things happen, waste might build up or your chemistry may fall severely out of balance. In these scenarios, a larger 40% - 60% water change is going to be the best resolution. Once things are back on track, return to your regular routine of 10% weekly.

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How To Perform A Water Change

Step #1 - Turn off your equipment. Everything that uses power should be turned off. Switching off the surge protector is an easy solution for getting everything all at once. You can damage pumps and heaters very quickly if they are left to run without water. 

Step #2 - Gather and layout all the gear you will need.  A bucket, siphon tube, a fill pump, plenty of towels (you will need more than you think), and your clean saltwater. 

**Pro Tip: You will spill water, be prepared to clean it up.

Step #3 - Now the fun begins. Start your siphon to start water flowing from the tank into your bucket.

Step #4 - Begin cleaning the sand bed using a gravel vacuum or siphon tube. When doing it weekly, you only need to clean a portion of the substrate.  Clean 25% weekly or something along those lines.  Remember, the idea is not to remove sand rather suck up the detritus in the sand. If your removing sand, slow down the siphon by pinching the tube. Also, do not overdo it...just clean the surface and only do a little each week.  If your sand bed is too clean, you can disrupt the biological balance in the tank.  

Step #5 - Never ever walk away from your tank while removing water. You WILL FORGET and spill water or flood your house. Using a timer to remind you every 5 minutes is not a bad idea.

Step #6 - Check the salinity and temperature of both your tank and new saltwater. If the new saltwater is more than 2-3° F colder than the tank water, you might want to heat it up to avoid stressing the animals. Adjust the salinity to match exactly.

Step #7 - Fill it up.  Move the clean saltwater into your display tank by slowly pouring it into the tank, sump, or filtration chambers. You can also use a fill pump and tubing, whatever works best for you. 

Step #8 - Turn on your equipment once you have filled up the tank. The water level is important and you may need to add a little more or remove a little water from the tank after your pumps are turned on.  Mark the water level using a marker so you know exactly where it needs to be after turning on your pumps and filtration. 

Tips & Tricks For Success

  • Scrape and clean algae from the glass and other tank surfaces before removing the water
  • Pull water from your sump, filtration chamber, and display. This helps remove detritus and algae that might be trapped in the filter chambers.
  • Leave your mechanical filter in the tank. Do not replace filter socks and pads until after you have completed the water change.  
  • Do your best to not expose coral to air when removing water from the display.
  • Don't overdo it when cleaning your sand bed.  As mentioned above, light cleaning is best to avoid disturbing the bacteria and animals that rely on the sand bed to survive.
  • **Pro Tip - Never ever walk away from a water change.