What is Dosing a Saltwater Tank?
In the saltwater aquarium hobby, the term "dosing" is used to describe the act of pouring additives into the aquarium. There are a variety of different additives that can be "dosed"; two-part supplements used to maintain water chemistry or pH buffers, liquid foods, phytoplankton, and even beneficial bacteria. Essentially any fluid that isn't plain water can be covered under the umbrella of dosing. The rate at which you dose your aquarium really just depends on the additives your using and the particular aquarium.
Methods of Dosing
Additives can be dosed manually by hand which entails measuring the fluid in an appropriate measuring cup and pouring it directly into your tank. This works best for things that are not required on a daily basis like amino acids or bacteria supplements because manual dosing becomes quite tedious when done every day and is especially risky if the health of the tank depends on said additives.
Alternatively, you can automate dosing with the use of a dosing pump which is a special kind of peristaltic pump that is built to deliver measured amounts of fluid. The most basic dosing pumps can be attached to run on a timer while the most advanced pumps can be programmed directly via an app on your phone. For example, you could program your dosing pump to deliver 10mL of a particular additive, every day at 7 pm.
Dosing pumps tend to be preferred by reef aquarists because most aquariums with LPS and SPS corals require frequent dosing of two-part solution or similar additives to maintain water chemistry.
What To Dose & Why?
Most commonly dosed when starting a new aquarium as a means of inoculating the aquarium with beneficial bacteria strains. Helps to speed up the process of establishing a nitrogen cycle in the aquarium but can also be used to maintain a healthy population of beneficial bacteria as the aquarium matures.
Water chemistry is critical in an aquarium, especially those that contain corals. The most common application in a reef tank is two-part dosing to maintain calcium and alkalinity levels but is also done to maintain the correct ratio of minor and trace elements. Without the right elements in the water, corals will ultimately suffer and eventually perish because they use the elements to grow.
Water chemistry additives are often used daily in a reef tank but the exact frequency really just depends on your particular tank. Different corals use different elements and uptake those elements at different rates so what is happening in your tank will be different than what happens in another. Testing your water chemistry regularly is the only way to dial-in your dosing regimen and know for sure that you are maintaining stable water chemistry.
Amino and fatty acids fill nutrient gaps the corals cannot acquire via food. The proper use of amino and fatty acids will support vibrant color and optimal coral growth among your corals. Typically used on a weekly basis or as a "food supplement" when feeding fish and corals.
It's BRS Recommended: Brightwell Aquatics CoralAminos
Live phytoplankton can be dosed to provide nutrients for small fish, corals, filter-feeding invertebrates, and microcrustaceans (copepods). This is considered optional for most reef aquariums and should be used carefully so as not to cause elevated nutrient levels. It's more like feeding the aquarium but the term "dosing phyto" is common in the reefing community.
Dosing live phytoplankton specifically has been known to support robust biodiversity and a natural food chain in the aquarium that is representative of what exists naturally.
In some cases, additives can be used to help reduce or control nitrate and phosphate levels in the aquarium. For the most part, using additives as a means for nutrient control is considered a more "advanced" method and not likely something you're going to do when first starting out. In fact, building and maintaining your aquarium in such a way that you don't ever need these additives really is the best approach anyway.
Carbon dosing and liquid phosphate removers are two ways you can use additives to help control nutrient levels.
Do I Need to Dose Everything?
No, not ALL saltwater aquariums are going to require all of these additives. What you need to dose into your tank really just depends on your particular tank, most of which revolves around your choice of corals and other livestock.
Soft Corals - Probably won't require any daily dosing; just add bacteria when you cycle the aquarium and perform regular water changes with a high-quality salt mix. Liquid foods and amino acids can be used manually if you wish but are not absolutely mandatory so long as the corals are getting food like Reef Chili.
Mixed or SPS Reef (LPS and SPS Corals) - Use bacteria to cycle the aquarium and integrate daily two-part dosing to maintain stable calcium and alkalinity levels as necessary. LPS and SPS corals build a stony skeletal structure using calcium and carbonate they acquire from the water. The more stony corals you have, the more they will consume and the demand grows as the corals get larger. As the tank matures, the amount your dosing will increase incrementally alongside the growth of the coral.
Liquid foods and amino acids can be used manually if you wish but are not absolutely mandatory so long as the corals are getting food.
The only way to know for certain that you are dosing water chemistry additives correctly is to test your parameters. Before dosing anything, you need to have reliable test kits and know what your parameters are. Simply follow the instructions for maintaining your target parameters (included with your additives) and verify parameters on a very regular basis moving forward.