Aquarium Chemistry

     Salinity is if not the most, one of the most important things to maintain balanced in your aquarium.

     Some take it for granted or don’t think of it as much, however, it can have detrimental effects to the organisms in your aquarium if it is not stabilized.

     Salinity affects all other elements in your aquarium. For example, Joe tested his aquarium today and the salinity was 1.025, his calcium was 420ppm, alkalinity was 9.0DkH, magnesium was 1320ppm. Joes tank is happy.

     Joe however, does not have an auto top off system (a system that automatically replaces the evaporated water in his aquarium with RO/DI water).

     The next day, Joe’s tank reads: 430ppm calcium, 9.6 alkalinity, and 1350ppm magnesium. He quickly thinks,  “that’s strange, I never added anything to the tank.

     The point is, salinity affects everything in the aquarium, and if salinity is fluctuating, so is everything else.

     This can stun growth and create stress for corals and also make it very difficult for you to balance your chemistry since salinity fluctuations can throw off your testing results.

     There is much controversy regarding magnesium and it’s importance in the reef aquarium. 

     Most say they don’t test it if calcium and alkalinity seem to be in line.

     This can be true to some extent.

     Magnesium is the third most abundant ion in seawater. The first being H2O and the second being sodium chloride (NaCl). More plainly put, salt.  

     Because of this, magnesium is greatly affected by salinity, as was explained before. Here at Reef Pro, we call magnesium, “The Wall”.

     If you can, imagine a brick wall with two different liquids, one at each side. If the wall is tall, the liquids cannot cross and do not come into contact with one another.

     However, if the wall begins to sink, eventually, the liquids cross over and mix. This is usually, when magnesium drops under 1200ppm and calcium and alkalinity precipitate.

     You will find yourself adding more of the two-part solution but the alkalinity and calcium will not rise.

     Once you correct your magnesium and bring it up to about 3 times that of your calcium, everything should balance out.

     As I stated earlier, some say if calcium and alkalinity is ok, then magnesium should be fine. I also stated this can be true but to some extent.

     The reason I say that is because I have also seen in some cases where the magnesium has dropped under recommended levels and the elements are still pretty steady due to the hobbyist compensating for the precipitation.


     Now, should you test your magnesium as often as alkalinity and calcium? No, I wouldn’t necessarily say that often.

     But I would recommend you test for it at least once every two weeks.

Calcium, Alkalinity and Their Relationship
     Calcium and Alkalinity are like the “Ying and Yang” of the hobby, if you will. They need to be constantly balanced, and one can affect the other.

     Many hobbyists have trouble finding this balance in the aquarium and it even causes some people to give up on the hobby altogether.

     It really is not that difficult, once you understand the characteristics and uses of these chemicals in the reef aquarium.


     There are many things that consume these elements in the aquarium, not just corals.

     Depending on the water you begin with, you may want to test and balance your elements before even adding corals. I will explain why in a moment.

     Many aquarists tend to run into some situations where they cannot balance their calcium and alkalinity.


     Some tend to be pretty common and fairly simple. Some not so simple but can be dealt with.

•    High Alkalinity, High Calcium
     Simply lower the dosage until the desired ranges are reached.

•    Low Alkalinity, Low Calcium
     First I would recommend testing your magnesium. If your magnesium is in the desired range, then simply elevate your dose until the calcium and alkalinity levels desired are reached.

•    High Alkalinity, Low Calcium
     In this scenario, add a calcium chloride solution such as Reef Pro Calcium to slightly elevate the calcium and lower your alkalinity.

•    High Calcium, Low Alkalinity
     This problem tends to be pretty common. Especially in newer or lower coral load tanks.

     Alkalinity is consumed at a greater rate in any reef compared to calcium. This is due to the fact that alkalinity is consumed by not just corals, but also by nitrogen creating bacteria that process the wastes inside of your tank.

     Not to mention some corals, while acclimating to your system, do not consume calcium. Your calcium consumption will not change until the coral begins to grow and consume. 

     Because of this you will need to use a soda ash solution such as Reef Pro Alkalinity to raise your alkalinity to the desired level and stop dosing calcium and raise your alkalinity dose.

     Do this until calcium begins to be consumed and lowers to the desired range. Once the calcium is in the desired range resume regular dosing.



 Reef Pro
933 South Military Trail E-6
West Palm Beach, Florida 33415
(561) 267-5937

The Number One Stop For All Of Your Aquarium Needs!