
So. I’ve noticed something while taking care of some of the reef tanks that i maintain for clients around town. Most people don’t understand their water At All. So today class is in session. We will be discussing PH, Alkcalinity, Calcium and Magnesium.
Calcium is one of the major building blocks for your reef tank. In natural seawater, it is about 420 ppm, so it comprises just under 1.2% by weight of seawater’s solids. In the ocean, this concentration varies do to changes in salinity, which cause the calcium to fluctuate just as the salinity does.
Calcium is very important in a reef aquarium as many organisms, including corals and coralline algae, take it up in order to deposit calcium carbonate skeletons. If it is not maintained at adequate levels, such organisms become stressed and can even die. I recommend that reef aquarists maintain calcium at 380-450 ppm.
Alkalinity is a complex measurement. It is not a “thing” in the water. It is actually the summation of many things, all of which together provide a particular chemical property. The reason that aquarists measure alkalinity is that in normal seawater, most of it consists of bicarbonate and carbonate. Bicarbonate is what corals use in order to build their calcium carbonate skeletons. Consequently, alkalinity is an indication of whether or not adequate bicarbonate is present in the water.
Normal to high alkalinity implies adequate bicarbonate, while low alkalinity implies that it may be in short supply. In the absence of any method of supplementing alkalinity in a reef aquarium, the water can rapidly become depleted of bicarbonate. Alkalinity’s depletion from normal to unacceptable levels can take only a day or two in some reef aquaria, although it can take longer in aquaria with a lower demand for carbonate. When the water’s bicarbonate is depleted, corals that deposit calcium carbonate can become stressed out and even die. I recommend that reef aquarists maintain an alkalinity of 2.5-4 (7-11 dKH).
Magnisuim is nessesary for the bonding of calcium ions to other calcium ions. That is the simple way to explain it. However, if your mag reradings are to high, then it will affectively “poison” the calcium ions. In other words, they start to take up to much space and the calcium carbonates can’t harden together. A reading of 1250 ppm is what your shooting for.
I hope that this got some of you heading in the right direction, and didn’t just confuse you. This stuff is important for your tank, and if your serious about keeping a reef tank, then you’ll have to spend some time on it.
That’s the bad news. The good news is that its all really simple once you take the time to understand it. To that end, I’ll be doing an article a week on the subject of reef chemistry.
Look for more from us next week.
Chris@Big Dogs