Alkalinity and Calcium testing - important for every marine aquarium
One of the biggest challenges that the new saltwater hobbyist faces is learning what aspects of weekly aquarium care need to be top priority. I often explain to people that freshwater is more time consuming than saltwater, but saltwater is more difficult than freshwater. Often this confuses people, who do not distinguish the difference. I would ask you, is it more difficult to walk 1 miles or is it more difficult to jog 1 mile without stopping? Walking a mile takes longer, but jogging a mile without stopping is more difficult and requires some degree of achievement.
When I say that keeping saltwater is less time consuming than freshwater, I would actually say it is far less time consuming. In fact, one of the challenges that I face is taking my systems for granted. A properly setup saltwater tank, utilizing a protein skimmer, live rock, and proper depth of sand bed, seems to run itself. The routine tests that people so often discuss, especially in freshwater, rarely if ever give a reading which is unpredictable or changing in an established marine system. Although many people test for ammonia, nitrite, nitrate, and pH, most of us would pass out from shock if the results ever changed from the prior week. Truth is, I almost never run these tests, because I know exactly what the results are going to be. The only exception is Nitrate, which I test monthly as a formality, but always find this result to also be <5ppm, if not zero.
This predictability can cause mistakes to be made by hobbyists who are not testing for alkalinity and calcium. We NEED a test that gives us an indication of the water quality inside our marine aquarium, and we need this test to tell us of upcoming problems BEFORE THEY OCCUR. In my aquariums, I consider these tests to be alkalinity and calcium. It does not matter what type of saltwater aquarium you keep, be it FOWLR or reef, you should be testing for alkalinity and calcium.
Before I move on, let me tell you this. I am not a chemist. In fact, I hate chemistry so much that in college, I substituted a Senior level Physics class to replace a Chemistry 101 lab. However, I do not have to be capable of explaining how Chemistry works to apply the concepts to my aquariums. I simply need to know what is important to test for and how to adjust the necessary levels to reach the results needed, as applicable to the marine aquarium.
Lets start with Alkalinity. I am going to keep this very basic, and would suggest that anyone looking for a more in depth discussion to read some of the material written by Randy Holmes Farley.
Alkalinity is a measure of buffering ions in the water. These buffers keep the pH stable by neutralizing organic acids present in the water. These organics are introduced into the water in many ways, including fish waste and food decay. Ultimately, by testing alkalinity we are able to see trends in how efficiently organics are being removed from our system, based on our filtration system, stocking levels, and feeding habits. The higher the fish load and the greater the amounts of food introduced, the greater the amount of dissolved organic acids present in the water, and the faster the buffering ions are depleted. The end result is a declining alkalinity.
Every aquarium experiences a declining alkalinity, and action is required by the fishkeeper to keep alkalinity within acceptable levels to prevent pH swings and stress. I aim to keep my alkalinity at 8-12 dkh. I do so by taking steps to reduce the depletion of the buffering ions, such as maintaining my protein skimmer in top working condition, rinsing filter pads daily to remove organics acids that bond to the filter pads, and replacing activated carbon on a regular basis. Despite these efforts, alkalinity slowly declines, and buffers are used to keep alkalinity in check. I use Kent Marine Super Buffer DKH on my aquariums. It is important to note that I am not using a pH Buffer. I use an alkalinity buffer to replenish lost carbonate and bicarbonate ions, as well as minor buffering ions such as borate and magnesium.
This brings us to Calcium testing, which provides us with even more information. Calcium is the major element in saltwater that bonds with carbonates and bicarbonates to form buffering ions. Calcium must be present at correct levels to allow for these buffering ions to be present in the proper ratios. Testing for Calcium allows us to determine how critical the results of the alkalinity test are. More on this in a minute.
Calcium is depleted from your water to form buffering ions, and is depleted by coral growth and coraline algae growth. Do not underestimate the demands for calcium that are placed on your system by coraline algae. For example, my FOWLR has much higher calcium needs than my reef tank, and I attribute this to the extreme growth of coraline algae in my FOWLR system. I aim for Calcium levels of 400-460ppm and use Kent Marine Liquid Calcium (calcium chloride) as a supplement to maintain calcium levels.
A bit of common sense can be applied to the test results, if both Alkalinity and Calcium test results are known. I suggest testing 2 times per week on new systems, and then weekly as the results take on trends. If both alkalinity and calcium levels are within the desired range, then no action would need to be taken. Frequent testing will allow you to gauge how long it takes for the levels to begin to drop. I use this guide for how to apply the results:
If alkalinity is low and calcium is high, then I add a buffer.
If alkalinity is low and calcium is low, then I add both a buffer and calcium. I prefer to add the buffer first and then wait 12 hours before adding calcium. In many cases, the fishkeeper will use a 2 part additive, such as B-ionic. In this case, adding both at the same time is typical.
If alkalinity is normal and calcium is low, then I do a water change and test both results again in 48 hours. This test result is very unusual, and is a huge indicator that more frequent water changes are needed. In this case, the minor buffering ions are out of balance with the calcium ions, which is why a water change is the best course of action.
I strongly encourage everyone to consider the alkalinity and calcium test kits as a required piece of equipment. In fact, if I could only have 1 test kit, it would be alkalinity. The results are so important and provide so much information about my system that I would never try to live without it. You have my word, if you are not testing alkalinity now, then give it a try. You will find that you are spending much less time on your aquarium care in the future, and the overall stability of the environment and health of your fish will be greatly improved. You will have a crystal ball into the future of your aquariums health, and will be able to make adjustments BEFORE problems occur.
I hope this helps to clear up some of the confusion that circulates on the forums. As always, feel free to start a thread in our Saltwater area if you have any questions or comments.
Thanks for reading & Happy Fishkeeping!
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