What Are The Proper Levels For A Saltwater Tank?

I mention in other articles that the key to success with saltwater tanks is consistency. That includes being consistent with tank maintenance and preventing your water parameters from fluctuating. Livestock in your saltwater tank will stay healthy when your levels are consistent.

So what are the proper levels for a saltwater tank? Here are some numbers:


  • Water temperature: 72-78 F
  • PH: 8.1-8.4
  • Specific Gravity (SG): 1.023-1.025
  • Ammonia (NH3): 0
  • Nitrite (NO2): 0
  • Nitrate (NO3): 1 – Reef tanks – <30 Fowlr tanks
  • Calcium (PPM): 350-450
  • Alkalinity (dKH): 8-12
  • Phosphate (PO4): <0.2 – Reef tanks – <1.0 Fowlr tanks
  • Magnesium (PPM): 1250-1350
  • Iodine (PPM): 0.06-0.10
  • Strontium (PPM): 8-14 – Reef tanks – 4-10 Fowlr tanks




Water temperature


Many saltwater fish and other livestock are sensitive to fluctuations in water temperature. For the most part, a good range of temperatures should fall within 72F and 78F. I like to stay close to the 78F mark. The key with temperature is to not let it bounce up and down. It is stressful to your livestock.

The best way to maintain a constant temperature is to have a quality heater. If you have a large tank, then multiple heaters may be required. Make sure the heater you choose is a suitable size and strength for your water volume. In order to prevent heater failures from drastically affecting the water temperature, you should consider using a temperature controller. They are very reliable and affordable. This is the one I currently use.

Temperature fluctuations also occur during water changes. Some people forget to match the heat of the new water that you are mixing with that of the main tank. Pouring in cold water will reduce your main tank temperature. The issue being that it is a rapid drop in temperature which is more harmful than a progressive drop over time. Rapid temperature drops or rises in a saltwater tank is never a good thing.




Without over-complicating things, PH is basically how acidic your water is. PH has a range for which you should aim for, a saltwater tank is between 8.1-8.3. If you can maintain a constant level of 8.3, your tank should do well. The thing with PH, is that whatever the number you choose to aim for, make sure it stays constant. A neutral PH value would be 7. Don’t use chemical buffers to chase PH level. Use a quality test kit to check PH and your test shows 8.2, then maintain that value.

Over time, your PH level will start to decrease. The best thing you can do to maintain the PH level is to perform water changes. A routine water change schedule will be very helpful in maintaining a constant PH value in your tank.


Read 10 Most important water parameters for reef tanks 

Specific Gravity (SG)


It is sometimes misunderstood that specific gravity and salinity are the same things. They are similar but not the same. When you mix your salt into the water, the actual salinity refers to the weight of the salt or contents of salt in the water. This is measured in ppt or parts per thousand.

Specific gravity measures the density of the water. The more salt in it, the denser it is. You can use a hydrometer or refractometer to measure specific gravity. The refractometer is recommended as it is more reliable and accurate.

The normal range for specific gravity is 1.023-1.025. Anything lower or higher than these values can be stressful to your fish and others.


Ammonia (NH3)


Ammonia is a toxic waste in your saltwater tank and any detectable amounts can be harmful. It will occur naturally as fish waste and uneaten foods get into the water column. For the most part, ammonia will be present when cycling a new aquarium. Once the ammonia reaches an undetectable level, it shows that your aquarium is cycled. An established biological filter will aid in removing ammonia from your tank. If you detect ammonia levels in your water, either it is not fully cycled or you have biological filtration issues. Ammonia should always read 0 on water tests or undetectable.



Nitrite (NO2)


Nitrite is another level to watch out for when cycling a new aquarium. As your biological filter cycles, it will go from the ammonia stage into the nitrite stage. Nitrite is an intermediate by-product of ammonia. You want nitrate levels to be 0 or undetectable.

If your aquarium is not finished the cycle, you will show levels of nitrite on your water tests. If your aquarium has finished the cycling process, and you are showing levels of nitrite on your water test, then you have a biological filter issue or perhaps have dead fish in your tank causing an increase in ammonia.


Nitrate (NO3)


Nitrate is one of those levels where you may have a fully cycled and established saltwater tank but still measure nitrates in the water. This is normal. Ideally, you want to have nitrate levels close to 0, but chances are you will always measure some levels of nitrate in your tank. Small amounts of nitrate show your biological filtration is working.

Over time it is common for nitrate levels to increase. The best way to remove nitrates from your aquarium is to perform a water change. Low amounts of nitrates shouldn’t harm much in your tank. The problems occur when these levels are allowed to climb too high. Some invertebrates can not tolerate high nitrate levels and can cause stress and illness. If you have a reef tank, aim to keep your nitrate level around 1-5 or less, if you have a FOWLR tank, aim to have under 5-30.

Marine Depot Aquarium Supplies



If you have corals in your saltwater aquarium, it’s important to monitor and maintain the proper calcium levels. Corals have skeletons made up of calcium and it is natural for them to use calcium to maintain their health.

Over time the calcium level in your tank will deplete as it gets used up. This essential nutrient must be replaced to ensure proper coral health. If your calcium level is allowed to fluctuate up and down, this will surely do harm to the corals. Many hobbyists will use a dosing pump to add specific amounts of calcium on a daily basis to maintain a constant level. You should aim to maintain a calcium level of 350-450ppm. My current reef tank is happy at a level of 420ppm.




Maintaining a proper level of dkh in your saltwater tank is very important. Alkalinity is basically the measurement of bicarbonate in the water which is crucial to the health of corals. Bicarbonate is the most crucial element in the building of coral skeletons. You will need to keep the alkalinity levels in the range of 8-12 dkh. It’s important to note that alkalinity affects PH as well. So fluctuations in alkalinity will cause PH issues as well.



Phosphates in a saltwater reef aquarium can be a nightmare. Phosphates will fuel algae and cause huge problems. Phosphates are something that occurs naturally and you want to keep under control. In order for corals to thrive and stay healthy, these levels need to be as close to 0 as possible. To measure the phosphate level in your tank, a reliable test kit is needed as you are measuring levels that are normally low. Some of the poorer test kits make it difficult to read with a basic color chart.

Aim to keep your phosphate level below 0.2. In order to keep your phosphates at a low level, perform a water change. There are also different phosphate reducing media you can use in a filter or media reactor.




Magnesium is an element that is essential for proper coral growth. It is not something that everyone will normally test for, but you really should. It is often overlooked and without the right level of magnesium, your corals will suffer.  Magnesium is essential to all organisms for biological functions and is very important to organisms that are skeleton building.

The normal range of magnesium in your saltwater tank is between 1250-1350ppm. 1250 is on the lower side and you will most likely find your corals will do better in the higher range around 1300-1350ppm. It’s important to point out that it is very difficult to maintain the proper calcium and alkalinity levels in saltwater without maintaining magnesium levels as well.




Iodine is one of those elements that are both essential and toxic at the same time. Iodine is considered an essential element used for cellular function and the transfer of nutrients within cells. According to That Pet Place.com, Iodine is utilized by corals for the synthesis of pigments, which allow them to adapt to varying light conditions and provide their tissue with protection from UV radiation.

Iodine needs to be maintained within the range of 0.06-0.10ppm. Excess levels of iodine can be toxic to your fish and corals. It has strong antibacterial properties and can kill off the bacteria that is so important to keeping a healthy salt tank.




Maintaining a consistent and proper level of strontium is important as it aids the growth of corals, coralline algae and other organisms that have a skeleton or shell, including clams. Strontium is very similar to calcium in terms of the benefits they provide. Over time the strontium level will deplete and must be supplemented to the tank to maintain consistency. If you have a reef tank, aim to have a strontium level of 8-14ppm. If you have a FOWLR tank aim for a level of 4-10ppm.

Of course, as with all the levels on our list, consistency is key if you plan to have a thriving reef tank. Don’t concern yourself with chasing numbers and making drastic changes if one or more of your levels are not perfect. Most times these drastic changes will cause more harm than good. Always adjust levels in small amounts over time and give your livestock time to adjust.


Thanks for reading!