Ideal Water Parameters
PH - 8.0-8.3
Specific Gravity - 1.023-1.025
Temp - 76-82
Calcium - 350-450
Alkalinity - 8-10 dKH or 3-4 meq/L
Ammonia - 0
Nitrite - 0
Nitrate - < 10
Phosphorus - As close to 0 as possible
Magnesium - 1250-1350
Strontium – 5-15
PH & Alkalinity
It is difficult to discuss PH without mentioning the relationship it has with alkalinity so both will be discussed here. PH is defined as a measurement of the concentration of hydrogen ions in the water. Alkalinity is defined as a measurement of water's ability to neutralize acids or buffering capacity or in other words the amount of acid necessary to change the pH of the sample to a specific value. Usually when people refer to alkalinity they are referring to carbonate alkalinity which is defined as the amount of carbonate and bicarbonate. Other factors that contribute to the overall alkalinity level include borate, silicate, phosphate, and hydroxide.
PH and alkalinity are in a direct mathematical relationship when the aquarium is in equilibrium with the carbon dioxide present in the air. Carbon dioxide is soluble in water as carbonic acid. When the aquarium is not in equilibrium with the surrounding air, this relationship can be slightly altered. For example, when using a calcium reactor, excess levels of carbonic acid are produced from the introduction of carbon dioxide which can equate to a very high alkalinity but a relatively low PH. On the other end of the scale, when using calcium hydroxide one can experience a very high PH and a relatively low level of alkalinity due the imbalance of the amount of CO2 between the aquarium and surrounding air. Levels of carbon dioxide can vary throughout the day by the organisms that create sugars via the photosynthetic process. When the sun sets or the lights turn off on our aquariums then the photosynthetic process ends for the day and carbon dioxide is released as a waste product of metabolism. This is the reason why PH levels can drop throughout the evening hours and why it is often recommended to operate a refugium on a reverse photoperiod. Providing aeration via an air stone can aid in providing CO2 equilibrium.
Fluctuations in the PH level should not exceed 0.2 within 24 hours. For example: If your PH is 8.3 during the photoperiod then the PH should not drop below 8.1 during the evening hours. An increase or drop in PH exceeding 0.2 within a 24 hour period can be detrimental to some corals.
Calcium
How do I Calculate My Daily Calcium Consumption?
Calcium consumption can be influenced by many factors including the types of corals kept in the system, the size and amount of the corals kept, and the choice of substrate to name a couple. Aquarists running a DSB sand bed will need to provide more calcium and alkalinity than aquarists who have chosen to go bare bottom.
An easy way to get a good idea as to the calcium consumption of your tank you will need to purchase a calcium test kit. First start by taking an initial measurement using the test kit and wait 24 hours. During the 24 hour period do not add any calcium supplements at all. After the 24 hour period has passed measure the level of calcium again. For example if the initial test showed a calcium level of 400 and 24 hours later the test reveals that the calcium has dropped to 375 then it is safe to say that your tank has consumed 25 ppm of calcium. This is by no means an 100% accurate test but if the test is repeated once a week over the course of several weeks then the total consumption can be averaged to give a good approximation of the average amount of calcium consumed daily.
Forms of calcium
Calcium Hydroxide – Normally found as Kalkwasser or Pickling Lime. Calcium Hydroxide can raise PH levels very rapidly and should be added in small frequent increments or steadily dripped into the system. It is a common belief that calcium hydroxide should be used solely to replace water lost due to evaporation but instead calcium hydroxide should be dosed until either the PH level has risen by 0.2 or the daily amount of calcium needed has been met, whichever happens first.
Pros:- Excellent source of calcium ions
- Very cost effective
- Aids in the precipitation of phosphates
- Enhances protein skimming via a process called saponification
- Raises PH which can discourage the growth of nuisance algae
- Dissolves easily in cold water
Cons:
- Requires daily dosing which can become tedious for some
- Can overshoot the PH if too much is added too fast
Calcium Chloride - Usually the form of calcium found in most 2-part liquid additives. Calcium chloride should not be dosed without some form of alkalinity dosing to help maintain the ionic balance.
Pros:
- Can rapidly increase calcium levels without increasing PH levels
- Easy to dose
Cons:
- The use of 2-part additives can become very expensive over time when compared to other sources of calcium
- Easy to overdose calcium chloride
- Can sometimes create difficulties in maintaining alkalinity levels
Calcium Gluconate – Often referred to as “sugar-based” calcium, calcium gluconate and is the oxidation product of glucose and contains 9.3% calcium (roughly one-third of the calcium found in calcium chloride).
Pros:- Useful for the rapid colonization of coralline algae
Cons:
- Not very productive for the growth of SPS corals
Passive Supplementation - Calcium provided through the dissolution of aragonite within the sand bed.
Pros:
- No daily maintenance required
- Provides slow and steady source of calcium
Cons:
- Usually does not provide enough calcium to be considered a complete solution
Calcium Carbonate – Dissolved with carbon dioxide via a calcium reactor.
Pros:
- Once the reactor is dialed in to a specific setting then ongoing maintenance is dramatically reduced
- Provides steady and consistent amounts of calcium and alkalinity
- Long term costs are reduced as compared to a 2-part additive
Cons:
- Excessive carbon dioxide levels can reduce overall PH. This effect can be reduced with proper aeration.
- High initial cost
Strontium
There is much debate over whether or not the addition of strontium supplements in reef aquaria is actually needed. It is known that strontium is used in the process of building calcareous skeletons but it is unsure as to whether strontium is required in the calcification process or it competes with calcium ions since the molecular structure of strontium is very similar to that of calcium. Another possibility is that one way for an organism to rid itself of potentially toxic strontium is to deposit it into a calcium carbonate skeleton.
Temperature plays an important role in the uptake of strontium in the calcification process. It appears that as temperatures drop, the amount of strontium deposited in the skeletons of corals increases.
Aside from the usual strontium supplements, strontium can also be found in calcium hydroxide (Kalkwasser). Calcium hydroxide is harvested from limestone which is basically the skeletons of corals from millions of years ago that have been compressed over time into what we know as limestone. It is believed that during that time period the ocean’s temperatures were cooler allowing for an increase in the uptake of strontium by calcifying corals, thus increasing the strontium levels found in calcium hydroxide today.
Magnesium
Aside from being the third most abundant ion naturally occurring in seawater, behind sodium and chloride, magnesium plays an essential role in the calcification process. Magnesium interferes with the process of calcium and carbonate precipitation, therefore allowing the levels of calcium and carbonate in the aquarium to be elevated to levels higher than where they would be without the presence of magnesium. Basically if you find yourself always adding calcium supplements to your tank but find that it is difficult to raise your calcium to the desired level then magnesium is most likely the culprit that is holding you back. In this scenario, adding more calcium will not raise levels until the magnesium level has been elevated. The same theory applies to alkalinity levels as well. From a reef keeper’s perspective, magnesium’s main role in the aquarium is to slow down the process of calcium carbonate precipitation.
The main sources of magnesium are water changes, calcium supplements, epsom salts, magnesium chloride hexahydrate, and even small amounts of magnesium are introduced to the aquarium via fish food. Careful consideration should be taken when using Epsom salts to raise magnesium levels as Epsom salts are comprised of magnesium sulfate and excessive sulfate levels are not beneficial to the aquarium.
Iodine
Iodine has long been believed to be beneficial to various reef organisms including but not limited to soft corals such as mushrooms and xenia, lps corals such as caulastrea, and macro algae such as caulerpa racemosa and chaetomorpha. Iodine also plays an important role in the molting process of crustaceans like shrimp, crabs, and pods. Iodine is often regarded as toxic in excessive amounts to the animals we keep in our reefs because of its antibacterial disinfectant properties and is effective when used as a dip for various corals including zoanthids (commonly seen as Lugol’s Iodine). Iodine is not to be confused with iodide. Iodide is generally considered more stable and less toxic when being used as a supplement in the reef aquarium. Iodide is generally supplemented as potassium iodide which is a colorless, odorless solution and has been reported to have a shorter shelf life as compared to iodine, which is usually easy to spot because of its color and is considered much stronger than its potassium iodide counterpart. Organic iodide is usually seen in the form of methyl iodide. Iodine is removed from the water column through uptake by the organisms we keep in our aquariums as well as the filtration processes, especially carbon.
Forms of Iodine
Lugol's Iodine
Pros:
- Long shelf life
- Useful antiseptic properties are good for dipping corals or swabbing infected areas
Cons:- Very concentrated, easy to overdose
- Regarded as "toxic" in excessive amounts
Potassium Iodide
Pros:
- Easy to use for daily dosing without fear of overdosing
Cons:
- Short shelf life
- Requires larger doses to raise and maintain iodide levels
- Not potent enough to use for dipping corals
References
Water Parameters and Basic Reef Chemistry
Linear Mode
