How Often To Test Water Parameters In Saltwater Tanks?

In this article, I will explain how often to test the water parameters in your saltwater tank along with some tips to make the process easier. 

One of the most important duties you need to include in your tank maintenance routine is water testing.

If you want to keep a marine tank healthy for the long term, testing your water parameters on a regular basis is crucial.

One mistake that many hobbyists make is not testing their water levels as part of your normal routines. Some people will only check for levels if there is a problem with the tank. 

Waiting until there is an issue with the tank is not the right thing to do. It’s best to be proactive and take care of any water concerns before they lead to larger problems.

Testing your water can be time-consuming, but it is one of the most important parts of keeping a saltwater tank.

Being able to correct any imbalances in the water parameters after testing is important for maintaining the water quality of your reef tank.


How often should you test water parameters?

You should plan to test the water levels once per week.

Although there are no set rules with the exact time to check, you should plan to add water testing into your regular routine. 

You can test the water more or less if you like. Keep in mind that the longer you put it off, the chances of something going unnoticed is higher. 

Some people choose to test every 2 weeks or include it on water change day. Whatever routine works for you is best.

If testing the levels once per week allows you to address any water quality concerns, then continue testing once per week. 

The most important thing is to test frequently and don’t wait several weeks between tests. 

Every time you perform a test gives you the chance to be proactive and correct any imbalances before they turn into bigger problems.  

Important water parameters to test for

There are certain parameters to test for that are important for the health of your reef tank. 

Here are 10 of the most important ones. 

  • Alkalinity
  • Ammonia
  • Nitrite
  • Nitrate
  • PH
  • Phosphate
  • Salinity
  • Calcium
  • Temperature
  • Magnesium

Others to consider:

  • Strontium
  • Iodine

Not all of these need to be tested every time you perform a test. You may only need to test Magnesium every 2 weeks for example. Iodine and Strontium can be tested less frequently. 

Also, there are certain ones you will want to test for more often. The temperature should actually be checked every day or a few times per day. 


What are the proper water levels for saltwater tanks?

The following numbers are the normal limits for each parameter.

  • Alkalinity – 8-12 dkh
  • Ammonia – 0
  • Nitrite – 0
  • Nitrate – 1 for reef tanks, <30 ppm for fish only tanks
  • PH – 8.1 – 8.3
  • Phosphate – <0.2 ppm for reef tanks, <1 ppm for fish only tanks
  • Salinity – 1.023 – 1.025
  • Calcium – 350 – 450 ppm
  • Temperature – 75 – 79F
  • Magnesium – 1250 – 1350 ppm
  • Strontium – 8 – 14 ppm for reef tanks, 4 – 10 ppm for fish only tanks
  • Iodine – 0.06 – 0.10 ppm


Reef tank parameters chart

water levels for saltwater tanks


Factors that affect water levels in reef tanks

There are a few main items that affect the water levels in your reef tank.

Water source

Always use RODI water only for your saltwater tank. Tap water can contain harmful substances that are toxic to fish and corals. Tap water will negatively affect your water levels. 

Corals absorbing calcium, alkalinity, magnesium

Over time, these levels will deplete as corals will absorb them. It’s important to test and replace these elements as corals use them up. 

Water changes

Following a proper water change schedule will allow you to fix water quality issues like high nitrate and phosphate while providing your tank with much-needed elements. 

Water evaporation

Water will naturally evaporate from your tank every day. The rate of evaporation will vary based on several factors. As your water evaporates, the salinity level will rise. It is important to have a proper water top off routine in place to prevent an unsafe salinity level. 

Adding livestock

Any time you add livestock to your tank, certain water levels can change. Higher bioload can cause poor water quality and an increase in nitrate, phosphate, and create many other problems. 

How to maintain proper water levels

There is no specific method to use that will automatically maintain perfect water quality. The proper water levels of a marine tank can be maintained in a few different ways.

Over time, certain parameters will change or be depleted as corals use up trace elements. You need to ensure these levels stay within limits as corals will suffer from a lack of elements.

Water changes are a great way to replace elements in the water. A good quality salt will provide many items that your tank will need.

Magnesium, Calcium, Alkalinity, are elements that will be replenished by performing a water change.

Not all salts are the same though so choose your salt according to your tank’s needs. Check out the chart to see the differences.

saltwater nutrient comparison


Dosing is another great way to provide essential trace elements back into your tank water as they get used up over time.

There are many different products available for dosing which you can do manually or automatically using a dosing pump.

This is the most convenient and accurate method to use. 

Using an auto top off or ATO, is an effective way to replace evaporated water in your tank. This will help to maintain the proper salinity level throughout each day. 


What testing kits should you use?

Hanna Calcium tester @ Marine Depot

There are many different types of test kits on the market today. Some are better than others. I recommend staying away from the lower end and cheaper test kits as they can give poor results. As water testing is so important, you want to have the most accurate information that you can in order to make the right decisions. A good quality test kit will give you the best readings possible.

The Hanna Instruments testers are very popular and are designed to give you the most precise readings. They are reliable and easy to use. 

Hanna testers are available at Marine Depot.

Red Sea test kits are another great option and have been a top choice for years. They can be purchased individually or in a complete kit. They are reliable and accurate. They have a bit of a learning curve but once you get the hang of it, they are easy to use. 

Red Sea test kits are available at Marine Depot. 



Performing water tests on a regular basis is an important aspect to keeping a saltwater tank. You need to know what your water levels are in order to keep your livestock healthy.

Although water testing can be a bit tedious, once you get into a routine with a test kit that you like, it becomes much easier to do.

Water testing is the best way to know if your tank is out of balance and needs your attention. How often you perform water tests is up to you, but once per week will allow you to keep on top of things and maintain a healthy tank.