An Easy to Follow Water Testing Schedule To Help You Get Started - A Handy Guide

Welcome to Simple Reefs. We are a brand new website designed to take the stress and expense out of starting your very own marine aquarium. We’ve been talking about marine aquarium test kits a lot, lately. Today, we are giving you an easy to follow water testing schedule to help get you started.

This article follows on from our previous entries into our feature on testing your marine aquarium’s water. You can catch up with anything you missed at the following links.

• The Importance of Test Kits To a Marine Aquarium
• Which Test Kits Should You Buy for Your Marine Aquarium?
• Why You Should Avoid Low Quality Test Kits
• Why High Quality Test Kits are a Good Investment
• Frequent Testing Can Help Prevent Problems

I decided that this article would be a nice little add-on to my previous article where we talked about how frequent testing can help prevent problems. After all, what’s the point of test kits if you aren’t going to use them and aren’t going to use them frequently.

A Marine Aquarium Water Testing Schedule

Testing your marine aquarium’s water frequently is absolutely essential to a healthy home for your fish, invertebrates, and coral. Some of the tests we list here are optional depending on your own tank. While certain tests are essential in some cases, others are far less of a concern if you have no coral or if you don’t have any LPS or SPS stony coral. I will put a little note wherever that is applicable.

There are a few things you are going to want to have to hand before you start your testing journey. The most important of which is a diary or logbook and a pen. You want to be sure to record each and every result that you get as well as the date that you got the result. You could also use an app to do this, there are quite a few that work really well.

Having this information constantly to hand is going to allow you to paint a long term picture of your aquarium’s health. You want to be sure that your test kits are of a high quality as we discussed in this article right here. It pays to make sure that you are storing your test kits as directed in the instructions.

You also want to make sure that your test kits are still in date and they haven’t been exposed to any kind of external pollution due to splits or breaks in the packaging.

When Should I Perform The Tests?

There’s a few schools of thought with this question. If you are not performing a water change and are just doing weekly tests, just perform the test a few hours after your aquarium’s lights have come on. This will give things like pH levels a chance to stabilise. Test before feeding as you don’t want all that food interfering with the test results.

If you are testing while performing a water change, then we have a few options. If you water change every week as many people do, that will tie in perfectly with your weekly testing routine. You then, simply, add in the bi-weekly, and monthly, checks as and when needed.

The two ways we can do this are to perform water tests before and after our water change, or simply test the water before the water change. Either way, there are a few things we need to test in our freshly mixed saltwater so read that part carefully. Best practices are going to be the most beneficial and are as follows.

Ideal Practice:

The most comprehensive and most thorough approach with the best accuracy is to:

1. Test your aquarium water: Get your baseline readings for key parameters ready to go before you change water. Do this after your lights have been on a few hours and check the following –salinity, nitrates, pH, and ammonia. If your aquarium is more advanced and you have stony coral, check alkalinity, calcium, and magnesium, as well but only if it falls in the schedule outlined below. You can also opt to check nitrites and phosphates though that is totally down to preference. Jot all of these numbers down.
2. Prepare your new saltwater: Mix your salt water as directed by the manufacturer. Most will benefit from a 24 hour wait period to allow the salt to dissolve and the water to stabilise. Some, like Aquaforest, are ready almost instantly.
3. Test your newly mixed saltwater: Again, this will depend on your tank. At the very least, measure its salinity and temperature because you want those to match the tank the water is being added to. If you have a tank with stony coral, you may want to measure other relevant parameters too like alkalinity, calcium, magnesium so that you can match your display tank’s target parameters. I like to measure my newly mixed water’s ammonia as well but that’s because I am paranoid after this happened.
4. Perform the water change.
5. Test your aquarium water again: Give it 24 hours after the water change to allow the tank to calm down and stabilise. You don’t want any kicked up muck or sand messing with your results. 24 hours is usually plenty to get accurate post-change readings. Perform the same tests again that you performed the day before depending in your schedule and tank type.
6. Log all your results: This is the most important step for long-term success, as it allows you to see trends and adapt your husbandry practices. This is where you will find out the impact your water change just had.

I’m not going to lie, that’s a lot of testing. It’s a great way to get a thorough picture of just how well your aquarium is doing and how your water changes are impacting it. It is incredibly helpful to have a before and after picture of where you are and what impact your husbandry is having on the tank.

Not So Ideal Practice:

The not so ideal and far less beneficial way to do things is to simply test the water before you perform the water change. These steps are as follows.

1. Test your aquarium water: Get your baseline readings for key parameters ready to go before you change water. Do this after your lights have been on a few hours and check the following –salinity, nitrates, pH, and ammonia. If your aquarium is more advanced and you have stony coral, check alkalinity, calcium, and magnesium, as well but only if it falls in the schedule outlined below. You can also opt to check nitrites and phosphates though that is totally down to preference. Jot all of these numbers down.
2. Prepare your new saltwater: Mix your salt water as directed by the manufacturer. Most will benefit from a 24 hour wait period to allow the salt to dissolve and the water to stabilise. Some, like Aquaforest, are ready almost instantly.
3. Test your newly mixed saltwater: Again, this will depend on your tank. At the very least, measure its salinity and temperature because you want those to match the tank the water is being added to. If you have a tank with stony coral, you may want to measure other relevant parameters too like alkalinity, calcium, magnesium so that you can match your display tank’s target parameters. I like to measure my newly mixed water’s ammonia as well but that’s because I am paranoid after this happened.
4. Perform the water change.
5. Log all your results: This is the most important step for long-term success, as it allows you to see trends and adapt your husbandry practices. This is where you will find out the impact your water change just had.

As you may notice, the only step we are skipping here is retesting the water after the water change. You may be wondering why we test the water before we perform a water change? Well, this gives us an idea of the changes that are occurring between our water changes.

We know what is going on in the tank after it has had some time to settle and stabilise. This way we can get an idea of whether we should perform a larger water change than we initially thought or dose more than we initially thought we needed to.

You are testing before to, essentially, guide how much water to change and how much you need to dose (if necessary). This isn’t ideal but it does save money and it is something that I do if I am confident that my tank is doing well.

The Water Testing Schedule

So let’s go, here is a schedule featuring tests for every day, once a week, every two weeks, and every month. Remember, not all of these tests will apply to every tank.

Daily Testing (optional but beneficial)

1. Temperature
   • Ensure it stays within your chosen range – usually 75–82°F (23.5–28°C).
   • Use a reliable digital thermometer.
   • I like to keep a thermometer with a saltwater proof probe in my tank and visible at all times. They are very affordable and only take cheap batteries.

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Weekly Testing

1. Salinity/Specific Gravity
   • Test with a refractometer. Hydrometers tend to be unreliable and imprecise.
   • Make sure you frequently calibrate your refractometer with 35ppt calibration fluid.
   • Target: 1.023–1.026SG (30.5–35 ppt).
2. pH
   • Maintain pH levels between 8.0–8.4.
   • Liquid test kits are cheap and fairly reliable. Cheap digital probes can be inaccurate.
3. Ammonia (NH3/NH4)
   • Should be undetectable (0 ppm).
   • Detectable ammonia can indicate a problem.
   • External cleaning products and things like cat litter trays can cause ammonia in your water.
   • Cheap test kits like API can be unreliable and give false positives for ammonia.
4. Nitrite (NO2) (Optional)
   • Should also be undetectable (0 ppm).
   • Indicates a properly cycled tank.
   • Not everyone checks nitrite as it is less deadly in a marine aquarium.
5. Nitrate (NO3)
   • Helps to maintain levels below 20 ppm for fish-only tanks or for soft coral; below 10 ppm for more advanced reef tanks; below 5ppm for stony coral tanks.
6. RO/DI Water Quality
   • Check the TDS (Total Dissolved Solids) level of the fresh water you are buying or producing using a RO/DI filter. You need to make sure it is 0 TDS, ideally. If it is higher, it may indicate that you need to change your filters. I have an inline checker that is connected to my RO/DI filter and check every time I use it.

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Every Two Weeks Testing

1. Phosphate (PO4) (Optional)
   • Target: Below 0.05 ppm for reef tanks; under 0.1 ppm for fish-only tanks.
   • Prevents algae outbreaks.
   • Optional but very helpful, particularly if you have a lot of algae.
2. Alkalinity (KH) (Reef Tanks)
   • Aim for 8–12 dKH.
   • Supports coral growth and maintains pH stability.
   • Mainly for reef tanks, particularly those with LPS and SPS stony coral.
3. Calcium (Ca) (Reef Tanks)
   • Target: 380–450 ppm for coral tanks.
   • Essential for coral skeletons and invertebrates.
   • Mainly for reef tanks, particularly those with LPS and SPS stony coral.
   • Many aquariums, particularly nano aquariums, should see the levels replenished by regular water changes. More advanced aquariums will need dosing.
4. Magnesium (Mg) (Reef Tanks)
   • Keep levels between 1250–1350 ppm.
   • Helps stabilize calcium and alkalinity.
   • Mainly for reef tanks, particularly those with LPS and SPS stony coral.
   • Many aquariums, particularly nano aquariums, should see the levels replenished by regular water changes. More advanced aquariums will need dosing.

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Monthly Testing

1. Trace Elements (e.g., Iron, Iodine, Strontium) (Advanced Reef Tanks)
   • Test if keeping corals or sensitive invertebrates.
   • Replace with supplements as needed.
   • Mainly for reef tanks, particularly those with LPS and SPS stony coral.
   • Many aquariums, particularly nano aquariums, should see the levels replenished by regular water changes. More advanced aquariums will need dosing.

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In Short

This handy testing schedule should be enough to cover all but the most advanced of marine aquarium needs. If you follow this schedule as laid out and keep the results jotted down, you should be well on your way to marine aquarium stability. Thanks for reading and spending your time with Simple Reefs.