8 Important Reef Tank Parameters (Ideal Ranges & How to Maintain)

Image Credit: Marine Depot via YouTube
Image Credit: Marine Depot via YouTube

8 Important Reef Tank Parameters (Ideal Ranges & How to Maintain)


One of the most important jobs of aquarists is to manage the water quality of their reef tanks. In order to do this, you need to have a basic understanding of the parameters needed for a successful reef aquarium.

This involves understanding the natural processes involved in the different compounds in your water and how they react to one another. However, some parameters are much more important and manageable than other ones.

Most important water parameters

It is crucial that you monitor the parameters to ensure that your tank’s ecosystem will not only survive but thrive. However, reef aquariums are complex environments with many moving parts, so there are going to be factors that you can more easily monitor and control; those are the important parameters as trying to measure and control the other parameters is often a lost cause in a home aquarium.

The most important reef tank parameters to closely monitor are salinity, calcium, alkalinity, nitrate, pH, phosphate, temperature, and magnesium.

Reef aquarium parameters spreadsheet

MojaveReefer over at created an INCREDIBLE Microsoft Excel spreadsheet for tracking water parameters. Many thanks to MojaveReefer for providing this file to the reefing community. If for some reason in the future it is unavailable from ReefCentral I’ve backed it up for posterity here.

Saltwater aquarium testing chart

Temperature (FOWLR)76 F82 F79 F
Temperature (Reef)76 F79 F78F
Nitrate0 ppm20 ppm5 ppm
Alkalinity7 dkh12 dkh9 dkh
Phosphate0 ppm0.1 ppm0 ppm
Calcium380 ppm450 ppm400 ppm
Magnesium1200 ppm1350 ppm1300 ppm

Using test kits

There are many test kits on the market and are a staple in all aquarists’ toolbox. The only way you will care for your saltwater tank accurately is to ensure that you test the water regularly and accurately. You don’t want to skip a test, and that week it turns out the water’s high pH resulted in some chemical burns on your fish.

Test kits can come in a lot of varieties for different parameters. The easiest thing you can do is find a mast test kit that allows you to test all the important water parameters. However, depending on the test kit, you might want to buy a specific test yourself. I know that there are some test kits on that market that can be incredibly frustrating to use, especially if you have trouble telling the difference between shades of the same color.

Master test kits are usually the best thing to buy first when you need all the tests, but as time progresses, you will find that you use some tests way more than other ones. In this case, the other tests will need to be purchased separately. It would be silly to spend money on a new master test kit every time you needed a pH test.

In addition to the tests required to measure the water parameters that we have outlined below, you should have an ammonia and nitrite test as well when your tank is newly set up. During the cycling process when beneficial bacteria is being established in your live rock and sand you will want to monitor these 2 parameters. Once the cycling process is complete ammonia and nitrite should remain at 0. Beneficial bacteria will break down ammonia into nitrite, and then nitrite into nitrate. You should watch nitrate from this point forward. If nitrate begins to rise you may want to begin testing again for ammonia and nitrite since they are the precursors to nitrate.

What is the saltwater aquarium nitrogen cycle?

If you are just starting a new reef tank, you have likely heard a lot about the nitrogen cycle. The cycling process is the first step in curating your new reef tank and is the process in which your tank starts to build up a supply of friendly bacteria that is beneficial to the overall health of your reef aquarium.

The process takes about 2-6 weeks, and that will depend on how you set up your saltwater tank, the size, live rock, your experience, etc. The process involves ammonia, nitrites, and nitrates, which should be rising and falling at particular stages of the process. This means that you have some opportunity to practice some of those test kits you bought because you need to ensure that your saltwater tank is moving along appropriately.

The first thing you will probably notice in your tank is that the ammonia levels rise significantly at first. That is completely natural and will begin to subside in time. Eventually, your nitrite will rise, followed by your nitrate, which will help to regulate the other two compounds. Once the nitrate rises, the ammonia levels should drop steadily. That shift from nitrites to nitrate is what you should be looking for. The bacteria we are trying to build up in the tank take the nitrite and turns it into nitrate.

You must keep to a hands-off approach during this process. That is because everything that is happening is a natural process that requires some time. If you were to disrupt this process by trying to lower ammonia levels, cleaning the tank, or something along those lines, you will have to restart the entire nitrogen cycle. The best thing you can do is let your saltwater aquarium do its thing and perform your tests.

Reef tank trace elements

Trace elements in your reef tank are elements that are common in natural seawater but make up a small percentage of the water. In fact, the trace elements only make up 0.7 percent of the total content of the seawater. Here are a number of examples of trace elements in natural seawater. This is not a complete list of all the trace elements that you will find in seawater but it will give you an idea of the kinds of elements you can find.

  • Cobalt
  • Iron
  • Iodine
  • Fluorine
  • Nickle
  • Tin
  • Copper
  • Zinc

You probably recognize a few of those names, and as shocking as it might seem, those aren’t even all the elements you will find in that 0.7 percent! Trace elements, despite taking up such a small percentage, are still really important for your tank’s water supply.

Since they are so important, it is possible you’ll need to perform dosing of these elements. Salt mixes include enough so that your water will start with the required trace elements needed for your reef aquarium inhabitants. A trace element in your marine tank will only become a problem if you have a really stocked tank and don’t regularly change your water. There are test kits for these different compounds if you are worried that you may be at lower levels than is recommended.

Ideal salinity level for a reef aquarium

Reef tank salinity target


Reef tank salinity range

1.022 – 1.027

I don’t think I have to explain this one too much. salinity is the amount of salt that is in your water supply. It is often measured as specific gravity using a hydrometer, but a refractometer can also be used to measure the salinity.

You should aim to have a specific gravity that sits at 1.025, but there will be times where you might want to have slightly lower or higher specific gravity depending on your fish and coral. A salinity range of 1.022-1.027 is acceptable but you should be striving to maintain 1.025 for best results.

How To raise salinity

The easiest way to add salinity to your tank is by adding an additional saltwater solution to your tank. However, just like other important water parameters, it is important that you don’t shock your fish and coral by changing levels too quickly. You should try to keep your salinity change to about 0.001 every day. This will guarantee that you are not going to overdo the changes to your tank, and your coral and fish will stay happy.

How to lower salinity

You might be able to guess the best way to lower the salinity. You can siphon about 10 percent of the water from your tank and then add the same water you would use when making your saltwater, but this time don’t add saltwater.

Ideal calcium level for a reef tank

Reef tank calcium target

400 ppm

Reef tank calcium range

380 ppm – 450 ppm

Calcium, the parameter even your nephew will be familiar with. Calcium, just like with human bones, helps corals grow since they are made mostly of calcium carbonate. For this reason, it is possible that your calcium levels will quickly deplete if you have growing corals. However, high levels of calcium are not going to increase the growth of your corals but low levels will impact coral health. High levels might also affect your alkalinity if you aren’t careful.

It is best to keep your calcium levels between 380 and 430 ppm. You may not need to worry too much about maintaining this parameter as it might seem like it is taking care of itself. That is because the salt mix that you use to make your saltwater often includes a lot of additional calcium. It is possible that your corals will work through this calcium though so more often than not, you will be working to increase your calcium rather than lower it.

How To raise calcium

Like we previously discussed, calcium is often supplemented through the salt mix that you use to make your saltwater. What this means is that every time that you perform a water change, the water is receiving a boost in calcium. However, what if you just performed a water change and the levels are not high enough yet? You could also buy supplements for your reef tank. Follow the manufacturer’s instructions for the correct measurements.

How to lower calcium

Lowering calcium might be one of the least convenient water parameters to fix since there are few options to do it. Water changes that are using a sat mix with little to no calcium would help solve the issue. As the calcium-rich water leaves the tank and is replaced by the new water, the levels should begin to drop.

Ideal alkalinity level for a reef tank

Reef tank alkalinity target

9 dkh

Reef tank alkalinity range

7 dkh – 12 dkh

Alkalinity is one of the most important measurements you can monitor in your tank. That is because alkalinity can be used to help us get a gauge on the overall health of the tank. Alkalinity has a direct impact on both the pH levels and the available bicarbonate.

Why does that matter? We will discuss pH shortly, but the bicarbonate that is available in your tank will dictate the health and growth of your corals. They use the compound to build their skeletons, so without it, they are completely out of luck.

The ideal alkalinity for your tank should be between 7-11 dKH. However, it isn’t simply the number range that you need to be consistent with. You shouldn’t be flipping between 8 and 12 every other day. That is a large difference and will shock the health of your marine tank. Try to stay steady within that range.

How To raise alkalinity

There are a few methods you can try to raise the alkalinity of your tank.

  • Baking soda is a great way to increase your alkalinity but use it carefully. You should try to limit drastic changes in your reef tank so aim to change no more than 1.4 dKH a day.
  • You can use a supplement (which often includes calcium) to increase your levels. Follow the manufacturer’s instructions and double-check your starting levels.
  • Soda ash is another great method of increasing your alkalinity. You can find soda ash online or at a local pet store. Like the other methods on this list, make sure to do it slowly and to follow the instructions.

How to lower alkalinity

Elevated alkalinity is one of the worst things, but you need to be careful in how you address it. Like calcium, there are few methods to lower your alkalinity, the main one being that you need to dilute the current levels. Using water with less alkalinity or water from reverse osmosis, perform changes to your water regularly.

That sounds easy until you realize that you won’t just be diluting the alkalinity in your tank. Other important water parameters will begin to be affected, so make sure you are checking your levels throughout the process.

Ideal nitrate level for a reef tank

Reef tank nitrate target

5 ppm

Reef tank nitrate range

5 ppm – 10 ppm

Elevated levels of nitrates can result in quite a few issues for you and your tank if you aren’t careful. High nitrates will begin to climb eventually in your reef aquarium due to the natural maturation process. depending on the growth, some of these nitrates can be dealt with by your corals, but sometimes that isn’t possible, which can lead to algae growth. Plus, there are types of invertebrates that can be negatively impacted due to the elevated levels of nitrate.

You should aim to keep nitrate in your reef aquarium between 5 to 10 ppm.

How To raise nitrate

Probably the only time that you would want to see the nitrate level to rise in your aquarium is during the nitrogen cycle. The best way to build up beneficial bacteria if you don’t already have some is to add organics that will break down. A common tactic some use when setting up a new tank is to add a single shrimp from your local supermarket. The shrimp body will begin to decay and bacteria will begin to grow. This will ultimately produce ammonia, then bacteria will convert the ammonia to nitrite, afterward the bacteria will convert the nitrite to nitrate.

For a less risky method, you can buy a supplement for your reef tank. All you would need to do is follow the manufacturer’s instructions but be careful to test the water parameters of your tank over time. Adding anything to your tank can be a gamble since it can create a chain reaction of chemical changes.

How to lower nitrate

The best way to lower nitrates is really common maintenance practices. For starters, watch how much you are feeding your fish. Overfeeding is one of the most common reasons for having elevated nitrates so ensuring the meal portions are small to reduce leftovers will help significantly. This in conjunction with keeping your tank clean and following regular water change routines will help to lower your nitrates and keep them there.

For a more proactive approach, consider getting more live plants. Live plants will use the nitrates for their own growth and thus help maintain lower levels. Remember that nitrate measuring above 10 ppm can drastically increase the growth of algae in your tank.

Ideal pH level for a reef tank

Reef tank pH target


Reef tank pH range

7.8 – 8.5

Your pH is simply the acidity of the liquid in which you are measuring. To ensure that your coral and fish are able to thrive within your tank, they need the pH of your reef aquarium to be within a particular range that fits their needs. The pH level can have drastic repercussions if you are not monitoring it appropriately. For instance, low pH could result in increased levels of ammonia which is one of the worst compounds to have elevated levels of due to its toxicity.

The ideal pH level for a reef tank is between 7.8 and 8.5 pH.

How To raise pH

Raising the pH in reef tanks is one of the easier water parameters on this list. There are several methods that can aid you in this task, but some of them might not be possible depending on your tank’s setup. Please read through the options carefully to ensure that the one you choose is the one that is best for your current situation.

  • Using a refugium – A refugium is simply a separate tank from your main display tank but still connected through the water supply. The refugium has a lot of potential uses but for our purposes here, it can be used to regulate your pH levels. Simply use the refugium to grow macroalgae. The macroalgae will help to raise the pH level in your reef tank.
  • Baking soda – Here is our best friend baking soda again. Simply use 1 teaspoon of baking soda per 5 gallons of water. Dissolve the baking soda in aquarium-safe water and slowly pour it in.
  • New decor – If you need to raise the pH of your tank, but you also were looking to add some more decoration, then you are in luck. You can add shells and rocks to help raise the pH in your reef aquarium. Crushed coral can be added to your tank (pretty much anywhere in case you don’t like the look of it), and it will help to increase the pH of your tank. Make sure to monitor your tank to see if the increase becomes too much. You might need to remove some of the crushed coral.
  • CO2 control – One of the biggest influences of increased pH in your reef aquarium is the CO2 that is present. The exchange of gases from water turbulence, protein skimmers, and even the air around the water can potentially influence the water parameters. There are a few methods you can try to influence the level of carbon dioxide in and around your tank. First, if it is possible, you can try to run an air tube from the protein skimmer to the outdoors. Just make sure the air tube isn’t somewhere problematic that could result in worse air being introduced to the tank. There are also devices called CO2 scrubbers which help to remove the gas from the reef aquarium water before it is introduced to the main tank. The only issue with using this device is that it can be too effective in some cases. Measure the reef tank parameters to ensure that your levels don’t cause you to go over your target pH level.

How to lower pH

You might be seeing a pattern at this point; lowering pH levels are much more difficult than raising them in your aquarium. Here are some methods that are effective in lowering your pH level.

  • Peat moss – This is most aquarist’s favorite method for reducing pH in their reef tanks. The moss reacts with the aquarium water by absorbing minerals and making your water soft, but at the same time, it releases compounds into your water that lower the pH. You can place the moss in your filter or even use it as substrate. It doesn’t matter how you choose to use it as long as you are comfortable with its placement in the reef tank. It does need to be in the tank for a little bit, as a simple dip won’t take care of your issue.
  • Add more CO2 – Just like how too much CO2 in your tank can result in pH levels so can too little CO2 result in low pH. You might consider investing in a liquid fertilizer for your live plants. This should help facilitate their growth as well as help increase the pH in your reef tank.

Ideal phosphate level for a reef tank

Reef tank phosphate target

0 ppm

Reef tank phosphate range

0 ppm – 0.1 ppm

Phospate doesn’t directly affect your fish but it certainly can help facilitate the growth of the plants in your tank including algae. In order to effectively prevent algae blooms, it is pretty important to measure your phosphate levels in your tank. Algae blooms can reduce the oxygen in the reef tank and affect the over-water quality thus hurting your fish.

The ideal phosphate level in your tank should be at the most 0.05 ppm if not less. That is because at 0.1 ppm algae growth is promoted and beyond that, it only becomes increasingly stimulated.

How To raise phosphate

It’s not likely you’ll want to do so, but if you are looking to increase phosphates for plant growth or trying to encourage a little more algae in your tank, then consider some of these methods to facilitate that growth. Take a look at the food you are using for your fish. You might be able to increase your phosphates by simply paying more attention to the food brand and how much you feed your fish.

Phosphates come from all sorts of sources like plant and fish, aquarium salts, and fish feces. I am not saying you should stop cleaning your tank to increase your phosphates because that will cause other issues, but knowing where they come from will allow you to better plan how phosphates enter your tank.

How to lower phosphate

An elevated phosphate level is never ideal so it is best to counter it as soon as possible. Here are a few methods to help reduce the phosphates in your aquarium.

  • Water change – The best way to manage the phosphate levels in your tank is to change the aquarium water regularly. Make sure you are addressing the original cause of the elevated levels, though, or you will never reach an optimal level.
  • Cleaning – Give your tank a deep cleaning. However, this can remove all the good bacteria that you have been building up in your reef tank and will require the most work on your part to complete effectively.
  • Phosphate absorber or phosphate binder – An absorber can be added to your filtration system. These are chemicals, so they generally should be one of the last options you consider.

The ideal temperature for a reef tank

Reef tank temperature target

78 F

Reef tank temperature range

76 F – 82 F

Temperature is probably one of the first water parameters that we begin to take into consideration since many of us are familiar with our first attempts at keeping fish as children. Typically, the fish in a reef tank will require a temperature range between 76 and 82 degrees Fahrenheit but some will require a much lower range than that.

Always double-check the needs of your fish and coral for the specific reef tank parameters. Depending on the climate of your home, you might not even need to invest in heaters but for most other people in the aquarium hobby, we need to invest in heaters to create optimal temperatures.

How To raise temperature

However, there are times where other factors cause our aquarium temperatures to rise or drop. During these circumstances, it’s important to know how to combat the temperature change. Unfortunately, there really is only one way to raise the temperature in your tank. You need a quality heater to keep your tank warm.

I say quality because the last thing you want is your heater to die out in the middle of the night and you come in to see your fish are frozen. Make sure you are checking your heater regularly to help mitigate the risk. Also, as useful as the digital thermometers can be, consider getting a floating thermometer in case of equipment failure.

How to lower temperature

Thankfully, there are more options for reducing the temperature in your tank. However, the method you decide upon should be based on the core reason that your tank’s temperature was elevated in the first place.

  • Ice – This might sound obvious, but it works and will give you time to fix what might be causing the temperature to rise in the first place. just float a bag of ice in the aquarium to reduce the heat but make sure that you are placing them in a bag, and don’t forget to measure the temperature. You don’t want to make your aquarium an ice bath!
  • Water changes – Water changes really do seem to be a cure-all. Performing small water changes can help to reduce the temperature as long as the water is cooler than the water in the tank.
  • Check your equipment – Equipment that can cause a tank to overheat mos often are the lighting fixtures and the heater. Turning one or both of these off can go a long way in reducing the elevated water temperature.
  • Adding a fan that can blow across the surface of your tank will help lower the temperature some. As hotter water rises and evaporates the fan will quickly move the hot moist air away allowing for quicker removal of the heat.
  • Install a chiller – If you are noticing that elevated water temperature is something you are consistently combatting due to lighting or your tank’s placement, then you should invest in chiller. The chiller will help maintain your aquarium at a consistent temperature.

Hydrometer &



Ideal magnesium levels for a reef tank

Reef tank magnesium target

1300 ppm

Reef tank magnesium range

1200-1350 ppm

Magnesium is important for coral growth and helps to maintain the alkaline and calcium in your aquarium. It is one of the most abundant minerals in seawater, so there are a lot of marine species that have adapted to using it.

The ideal range for your magnesium to sit at is between 1200-1350 ppm. Typically, the magnesium in your tank isn’t something you have to worry about too much, but it can still be a factor for much more important water parameters.

How To raise magnesium

The best way to increase your magnesium in your tank would be to purchase some supplements. These supplements can be found at most pet stores.

You may want to consider checking your salt mix and ensure that it has magnesium if you’re struggling to maintain good magnesium levels. Water changes with a quality salt mix are the primary way magnesium is introduced regularly into your reef tank.

How to lower magnesium

Magnesium that is above the 1200-1350 ppm range usually isn’t too much of a problem, but if you are testing above 1500 ppm, it often means that there is a serious issue since it is incredibly difficult to exceed this range due to its natural presence in seawater. However, if you find that you have elevated magnesium, you will need to perform water changes to get the reading you’re looking for.

Final thoughts

As you can see, aquarists have a lot to manage when it comes to the parameters of their reef tank. From ammonia spikes during the natural nitrogen cycle to unexpected rises in pH or salinity, developing a standard care routine for your reef tank is crucial. You never want to miss an important test day where you should have caught the failing levels of your temperature. Once you develop your routine, it becomes second nature to follow up on the different aspects of your tank’s needs.

As long as you are methodical and maintain the ideal levels for your saltwater aquarium, you are going to see success. Over time, you will create your own system and maybe even pick up your own tricks for how to manage reef tank parameters, and that is part of the beauty of the hobby. We all work together to further advance the care of our aquariums.

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