Saltwater Aquarium Supplements

Updated August 12, 2019
Author: Mike - FishLore Admin
Social Media: FishLore on Social Media

There are many different saltwater aquarium supplements on the market now. Which supplements are worth it? Which are snake oil?

Saltwater is comprised of many elements at different concentrations or Parts Per Million (PPM). Most saltwater mixes strive to replicate these ratios in their mix, although the various salt mixes have slightly different concentrations of certain elements. All of these elements that make up saltwater are vital to the health of the fish and corals we keep. Through the course of running your aquarium some of these important elements are depleted and will need to be replenished through water changes and possibly saltwater aquarium supplements.

How do you know if you need to supplement your saltwater aquarium? Well, it is our opinion that if you primarily keep fish and you perform frequent small water changes, then you may not need to supplement. Those frequent partial water changes are replenishing these depleted elements. However, if you're keeping corals or other invertebrates that need constant, high calcium levels for example, then you may need to supplement. This is where aquarium test kits are a necessity.

We recommend using a test kit if you plan on using any of these saltwater supplements. How can you know if you're adding too much or not enough without testing? Overdosing with one of the elements can be a serious matter, stressing your fish and corals. To rectify an overdose you would need to perform a large water change which could further stress these animals. Test, test, test. You never want to just start supplementing willy-nilly. It would be far better to just perform a partial water change to replace these used up elements. The salt mix will have these elements in the proper proportions.

Now, whether using these supplements is of any great benefit is up for you to decide. Is it just another way for companies to nickel and dime us? If you're running a fish only or fish only with live rock (FOWLR) tank, then you may not need to supplement if you're staying on top of your water changes. However, if you're keeping corals or other inverts that need constant and steady high calcium and alkalinity levels, then you very well may need to supplement with Calcium, Magnesium and/or Kalkwasser.

Here is a summary of some of the most common supplements:

Calcium Supplement
The primary element needed for clams, corals and some algae, Calcium (Ca) is needed for these organisms to grow. Natural Saltwater has a range of approximately 380 - 450 mg/L and it can be difficult to keep this level up in an aquarium with calcium consuming corals, clams and algae. There are various ways to keep the calcium levels up. Some popular ways include the use of Kalkreactors that dose kalkwasser and Calcium reactors to dose calcium. You can also purchase diluted calcium chloride (easier but kind of expensive) and dose that way. The problem with dosing liquid calcium is that you have to also use a buffer (carbonate or bicarbonate) when you dose calcium or you risk lower the alkalinity levels. There are two part calcium/alkalinity solutions and you should look into these products if dosing this way interests you.

Alkalinity Supplement
Why is alkalinity important? Well, alkalinity is basically a measurement of how well the water in your aquarium can buffer against a drop in pH. The alkalinity test will measure the levels of elements such as carbonates, bicarbonates and some other elements. Carbonate Hardness is often used interchangeably with the term Alkalinity, but the two are really not quite the same. Carbonate Hardness measures just the carbonates and bicarbonates while Alkalinity measures those elements and a few others. Natural saltwater measures an alkalinity of approximately 2.5 meq/L and carbonate hardness measures at 6 - 7 dKH. You may be wondering about the two different units of measurement being used here. Alkalinity is usually measured in milliequivalents per Liter (meq/L) and carbonate hardness is usually measured in degrees of carbonate (dKH). You can convert meq/L to dKH by multiplying meq/L by 2.8.
For example, 2.5 meq/L alkalinity = approximately 7 dKH, using the conversion 2.5 meq/L x 2.8 = 7 dKH.

Kalkwasser Supplement
This is a German word, that translated means "lime water". Kalkwasser is calcium hydroxide that is usually administered using a dosing system. The dosing system can be automated whereby the dose is controlled by the pH levels in the aquarium or it can be a manual process of dosing kalkwasser during water-top offs or slow-dripped into the aquarium. The good thing about kalkwasser is that it will supplement both calcium and help keep the alkalinity level and the pH stable.

You need to be careful when working with kalkwasser because the powder is fairly caustic. Gloves and an inhalant protector is a good idea when working with this product. It is recommended to use "purified water" which is basically water treated via Reverse Osmosis. You then mix about a tablespoon of dry kalkwasser to 1 gallon of water. Certain powders call for different amounts, so read and follow the directions carefully. After mixing, let the solution sit for a few hours so that the solution settles and any undisolved powder settles to the bottom of the container. You can then begin dosing the clear kalkwasser at a very slow rate, such as 1 drop every 4 or 5 seconds. You need to dose slowly because the pH of kalkwasser is around 12 and it could cause shock to the tank inhabitants.

How much you need to dose depends on how much calcium is being used in your tank. You need to get a calcium test kit and test the calcium level every day for several days in order to get a clear picture as to how much is needed. Test the pH, Alkalinity and Calcium levels while dosing too. After several treatments you'll develop a good idea as to how much and how often you'll need to dose kalkwasser. Some folks use it in all their top-offs and others do it a couple times a week. It really depends on the needs of your tank water.

Magnesium Supplement
In natural saltwater, Magnesium is in the range of 1200 - 1300 ppm. It is important to maintain a level similar to this range because magnesium helps maintain higher levels of alkalinity and calcium. Frequent use of kalkwasser reportedly lowers magnesium levels.

Strontium and Molybdenum Supplement
These two saltwater supplements, Strontium and Molybdenum, come in the same bottle. In natural saltwater, Strontium is in the 8 ppm range and Molybdenum is around 0.01 ppm. Strontium is important because it helps the growth of calcerous algae and Molybdenum is an important element because it used in the growth of the symbiotic algae in corals.

Iodine and Iodide Supplement
In natural seawater, Iodine occurs at 0.06 ppm. It is important to supplement iodine because it is quickly used up by the tank inhabitants and the protein skimmer. Invertebrates use it to molt and it helps corals with calcification. Lugol's Solution is a concentrated form of iodide and iodine and you usually administer 1 drop per 25 gallons of water. Lugol's is usually cheaper in the long run to use than the diluted forms of iodine supplements. Iodine supplementation can be controversial. Some hobbyists swear by it and some swear at it. We use it primarily for the benefit of the cleaner shrimps in our tanks and we tend to under dose. Lugols calls for 1 drop per 25 gallons, so in a 55 gallon tank we'd only use 1 drop.

Again, please get a test kit and test for the concentrations of these elements before you dose with these saltwater supplements. Remember, if you only have a fish-only or a fish-only with live rock tank (FOWLR) you may not need to use these supplements since you are replenishing them via the water changes. Reef tank keepers may have to seriously consider using them.

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