This article is sponsored by @Triquatics

The periodic table of elements.

This is a royalty-free image from Pixabay, courtesy of geralt.

The most important part of your tank is the water. Keeping a reef tank is like keeping part of the ocean in your home, and we all know that the ocean is a complicated beast! Maintaining proper parameters that are close to what your inhabitants would be experiencing in the wild is essentially what the reefing hobby is all about. There are many different “just right” parameters that reefers swear by, and we can’t argue with success. Testing your water is an important step to keeping your tank alive and healthy. We recommend testing your water with every water change, and in some situations weekly!


The first and most obvious test that we perform is temperature. Checking your temperature should be done almost every day to be sure that your systems are operating correctly. Like many things in the reefing community, the ideal parameters for temperature are widely debated. We’ve found that somewhere in the range of 76℉-82℉ is ideal for most reef tanks. Thermometers are one of the “needs” for your tank and can be as simple or complex as you desire. There are many options available for automating your temperature control which will activate heaters or chillers depending on your needs.


Calcium is another important parameter to test. Many corals have calcium-based skeletons. The corals create their skeletons from the water they are in and “suck” the calcium from the water, therefore causing the levels to drop and stunting their growth if the calcium isn't replenished. Again, we recommend sticking with natural levels (380-440 ppm or parts per million) as anything over that does not speed up the growth process. There are several ways to maintain calcium levels, the most common being a calcium and alkalinity additive which is known as two-part dosing.


Salinity levels in your tank are incredibly important to monitor, especially after water changes! Salinity is measured in a few different ways, either in parts per thousand (ppt), as specific gravity (sg), or as a function of conductivity which is in units of mS/cm or milliSiemens per centimeter. We believe that it is best to have your salinity at the natural level of 35 ppt (specific gravity of 1.0264, or conductivity of 53 mS/cm) to maintain the proper level that your inhabitants demand.

There are some who believe that keeping your salinity lower reduces the stress on your inhabitants but we do not feel this is necessary. We recommend testing your salt levels every time that you are topping off your tank, as well as every water change. Remember, when water evaporates it leaves behind the salt in your tank, you do not need to add salt water to your tank when you are topping it off as the salinity level will rise!


Alkalinity is the second half of the coral building structure. Alkalinity is simply the measurement (Milliequivalents Per Liter, shortened to mEq/L) of the capacity of water to resist changes in pH that would make the water more acidic. Sometimes alkalinity is noted in degrees of carbonate hardness, shortened to dKH. Alkalinity and calcium are often grouped together as the presence of one affects the use of the other by corals.

Contrary to calcium, alkalinity levels higher than normal can make coral grow at a quicker pace, although this may have negative consequences such as extra calcium carbonate growth on heaters or pumps. We recommend that you keep your alkalinity levels around 7-12 dkH. It is best to check this when doing water changes or if you are planning on starting two-part dosing.



Another important level to monitor in your aquarium is pH. The level of pH, or the relative acidity or alkalinity of a substance, can directly affect the health of your tank’s inhabitants. There are many schools of thought when it comes to pH control, all of them have merit and depending on your situation can be right for you. pH can directly affect the calcification process of your corals. Generally, staying right around the natural level of 8.0-8.5 is a good idea. In nature, these levels can fluctuate to levels that can even be stressful to some organisms, which makes it difficult to judge what are exactly the right levels. Reefs can succeed in varied conditions so it's all about what will work for your tank!


Magnesium is another key player in the mix. Magnesium directly affects both calcium and alkalinity levels. When magnesium levels drop, calcium precipitates out of the water which also causes alkalinity levels to fall. In situations where alkalinity and calcium are struggling it is best to start by checking magnesium levels, as it can often be overlooked. As with most levels in your tank, it is best to stick with the mixture that is found in nature, in the case of magnesium that level is around 1200-1400 ppm.


Phosphate is something else that is often tested for in test kits. Phosphate is found in the natural world; however, its levels are often very low. Phosphate in abundance can cause several issues, the main being excess algae growth and stunting the growth of corals. We recommend keeping phosphate levels below 0.03 ppm. Phosphates can often be eliminated before they are even introduced to your tank by using RO (reverse osmosis) filtered water.


One of the more toxic levels to monitor is ammonia. Levels that are above 0.2 ppm can potentially be dangerous to your inhabitants and we recommend that you keep the level at an undetectable rate! Ammonia becomes less of an issue in an established tank, but it is still wise to check the level on occasion!



In the same light, nitrite is something that many reefers fear as it is also toxic in large quantities (these fears may come from the freshwater hobby where nitrite is more of a problem). Fortunately, in an established reef tank nitrite is virtually non-existent. Many recommend not even testing for it once your tank has cycled and become established. Read more about CYCLING A TANK


Nitrate, on the other hand, is something that should definitely be monitored! An abundance of nitrate is often the cause of excessive algae growth and can even kill some invertebrates. It is generally advised to keep levels below 0.2 ppm or even closer to zero if possible. In the event that it goes over 0.2 ppm, general water changes using proper salinity will help, along with other processes such as a skimmer.


Strontium, like calcium, is a sort of building block for corals, and some believe that having larger amounts can supplement larger coral growth. As with almost everything we’ve listed, we believe it's best to stick close to natural levels. We recommend levels around 8 ppm, and not to supplement unless it has gone under 5 ppm. Strontium levels can often be adjusted with regular water changes if it goes beneath levels that are acceptable.


There are several different forms of iodine, and dosing and monitoring iodine in your tank can be quite complex. Many recommend that you do not dose iodine unless you have a specific reason for doing so. Some macroalgae use iodine for growth, but some believe that adding more does not help speed up their growth.

Iodine in crystal form.

This is a royalty-free image from Pixabay.


Maintaining your small part of the ocean requires careful monitoring of the systems that are found in nature. For most situations, we believe that keeping your tank as close to nature as possible to maintain a consistency that is sure to keep your inhabitants happy and healthy. Monitoring your tank while dosing and supplementing when necessary will ensure you have an incredibly healthy habitat!


This article is sponsored by @Triquatics


We encourage all our readers to join the Reef2Reef forum. It’s easy to register, free, and reefkeeping is much easier and more fun in a community of fellow aquarists. We pride ourselves on a warm and family-friendly forum where everyone is welcome. You will also find lots of contests and giveaways with our sponsors.


Author Profile: @Triquatics

Triquatics was founded by three reefers who believed that there could be a superior digital shopping experience worldwide!

They strive to offer a superior customer experience, the products that we all know and love, and a family atmosphere that keeps you as their priority. Unique Aqua Cash lets you earn money while you shop. Along with free shipping, no restocking fees, price match guarantee, and a 10% military discount, they are dedicated to providing you with the experience you deserve.