The Big 3 Ca, Alk, Mg

The Big 3
Ca, Alk, Mg
Maintaining parameters in the aquarium
• Used by corals to build hard skeleton base
o Corals need calcium carbonate to build their skeletons
• Used mostly by SPS and LPS corals and hard algae
• Proper range in the aquarium: 400ppm to 450ppm
• Can be tested with most commercial test kits
o API, Salifert, Hanna, Red Sea…
• Total alkalinity is defined as the amount of acid
required to lower the pH of the sample to the point
where all of the bicarbonate [HCO3-] and
carbonate [CO3--] could be converted to carbonic
acid [H2CO3] – Randy Holmes-Farley
• An indirect measurement of the amount of
carbonate in the aquarium
• Used by all corals along with calcium to build their
skeletal structures
• Proper range in the aquarium: 8dKh to 10dKh
o 2.86 meq/l to 3.57 meq/l
• Can be tested with most commercial test kits
o API, Salifert, Hanna, Red Sea…
• Works inversely with calcium
o As alkalinity goes up, calcium goes down unless a proper balance is kept
• If alkalinity gets too high too quickly it will
precipitate calcium in the water
o Looks like it is snowing in the aquarium
o It takes months for corals to adapt to new alkalinity so rapid changes can
cause Rapid Tissue Necrosis (RTN), Slow Tissue Necrosis (STN), or slow/no
• Used by all life in the aquarium
• Helps maintain a proper balance between Alkalinity
and Calcium
• Higher magnesium prevents alkalinity and calcium
“swings” in the aquarium
• Proper range in the aquarium: 1350ppm to
• Higher Mg can cause Calcium to be “super
saturated” in the tank
o This is a good thing!
o More calcium and more Alkalinity leads to better coral growth
• It is VERY important to maintain proper and stable
levels to having a thriving reef
• There are numerous ways to maintain these values
o Frequent water changes
o Calcium Reactor
o Dosing
Water Changes
• Used in a low demand tank (few LPS and SPS corals)
• Can be done daily (automatically) to maintain any
• Pros
o Helps stability in the tank
o Other bad stuff is removed during a water change
o Adds other trace elements needed by all life
• Cons
o Too much time!
o Tedious
• When doing water changes make sure your new
water has the correct levels of these 3 components
o Not testing the new water can lead to low levels over time
Calcium Reactor
• A way to “recycle” coral skeletons back into the system
• Media is dissolved in low pH water to replenish all
elements needed by corals
• Pros
o Keeps Alk and Ca at proper levels
o “Set it and forget it”
o Low maintenance once it is up and running
• Cons
o Normally only for larger tanks 75+ gallons (smaller tanks may have low pH
o Reactor failure can kill your entire tank
o Initial setup can be tricky and frustrating
o Many people use Kalkwasser to offset low pH issues
o May still need to dose for Magnesium in high demand tank
• Maintains proper levels by adding pre-mixed
chemicals to aquarium
• Calcium – Calcium Chloride
• Alkalinity – Sodium Carbonate
o Baking Soda
• Magnesium – Mg Sulfate, Mg Chloride or a combo
o Espom Salts
o Adding too much may raise the salinity of the tank, so be sure to test
• Various companies make pre-mixed 2-part products
o Some contain more than just Ca and Alk which may help other areas
• Can be added manually each day or use a
mechanical doser to automate
• Pros
o Finer control over all 3 parameters
o When done with a doser, parameter remain very stable
o When using a doser, chemicals can be added in small amounts 24 times a
day limiting swings in parameters
o Wider variety of dosers on the market now so prices will come down
• Cons
When done manually parameters may vary too much
When done manually precise measurements are difficult
Doser requires regular maintenance to verify it is still working properly
Chemical containers need to be refilled monthly
Chemicals can become costly over time
Accidental over-dosing can cause huge problems
Determining amount to dose can be tedious in the beginning
• Determining how much to dose
o Be sure parameters in the aquarium are at normal levels
• If not, add chemicals manually until they are correct
o Wait 3 days, don’t add any chemicals to the tank
o Test all 3 parameters
o Using a reef calculator determine how much chemical you will need to
o Divide that amount by 3. This is how much you will need to dose each
o After 1 week re-test all 3 parameters and verify they are still correct
• Modify doser settings as needed
• Tips and Tricks
o Do not dose both parts at the same time
• This can cause calcium to precipitate out of the water
o Do not dose both parts in the same area of the tank
• Do not dose near a return pump
o Split dosing up to small increments to limit alkalinity and pH spikes
o Check the doser after each water change to verify it is still working
properly and doesn’t need maintenance
• Tubing isn’t clogged
• Check valves still work properly (if used)
How To: Dosing Two Part in Your Reef Tank

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