Reef Tank Dosing (Guide)

Reef Tank Dosing (Guide)


Dosing is essential for maintaining calcium and alkalinity and other minor elements in reef aquarium water to ensure that demanding corals have the elements found in natural seawater required to be healthy, grow quickly, and maximize vibrant coloration.

Supplements aren’t necessary for FOWLR tanks and most soft corals or even tanks with some LPS (Large Stony Polyp) corals. However, it becomes vital for reef tanks containing SPS (Small Stony Polyp) corals, especially those with a dense amount of SPS corals.

Regular weekly water changes using a high-quality salt mix will provide enough replenishment of the major and minor elements for most saltwater aquariums that you don’t need to concern yourself with the added expense and complexity of dosing.

Even SPS tanks can get away without supplements in the first year to 18 months. However, as SPS corals grow and demand elements to maintain healthy growth increases, it becomes crucial to begin supplementing elements to meet these needs.

If you have more demanding corals or are considering adding some to your reef tank, keep reading to learn everything you need to know about dosing.

Reef Tank Dosing

Reef Tank Dosing is the process of adding supplemental elements such as Calcium, Alkalinity, Magnesium, and Trace Elements to your reef aquarium water. The purpose of Reef Tank Dosing is to provide SPS corals with the elements they need to grow and thrive.

Is dosing a reef tank necessary?

Most reef tanks don’t need to have elements dosed. Most premium salt mixes replenish calcium and alkalinity and minor elements that corals and coralline algae need to grow and thrive. The exception to this is SPS corals. Small-Polyp Stony corals are much more demanding and will need calcium and alkalinity and magnesium, and other trace elements dosed to ensure they thrive.

It will take 12-18 months before this becomes necessary for most reef tanks with a large amount of SPS coral. SPS frags and smaller corals will generally grow well, initially pulling the elements they need from the elements in premium salt mixes. Once they get bigger, it’s time to consider supplementing elements, or your SPS corals will begin to suffer.

What Should I Dose in my Reef Tank?

3 Main Elements

The 3 main supplements to pay attention to when it comes to dosing in a reef tank are:

  • Calcium
  • Alkalinity
  • Magnesium

These 3 elements should be the focus of your supplement schedule. And also, be tested regularly to ensure that you’re keeping them within the desired range. Calcium, Alkalinity, and Magnesium are the most critical ocean water components to ensure good coral health.

What Trace Elements Do Corals Need?

Many minor elements need to be replenished in demanding SPS coral-heavy aquariums.

Here’s a list of some of them:

  • Barium
  • Boron
  • Chrome
  • Cobalt
  • Iodine
  • Potassium
  • Iron
  • Copper
  • Manganese
  • Nickel
  • Strontium
  • Zinc
  • Bromine
  • Fluorine
  • Lithium
  • Molybdenum
  • Selenium
  • Vanadium
  • And many more…

Hardcore SPS reefers may get very detailed and track some of these, but most don’t need to bother. Regular water changes should replenish essential minor elements assuming you’re using a premium-grade salt mix for your saltwater.

Certain minor elements can significantly improve coral coloration. Red Sea’s Coral Coloration Program is a trace element supplement explicitly designed for this purpose.

For those who want to test for trace element levels, ICP testing is the best way to do so. ICP testing involves taking a sample of your saltwater and sending it to a lab for a thorough analysis.

This isn’t practical to do weekly. However, it’s reasonable to do it once every 6 months or every year to ensure that minor and minor elements are within acceptable ranges and that there isn’t anything significantly out of balance.

Red Sea Calcium Pro

Calcium Test Kit

If you want excellent accuracy, I highly recommend the Red Sea Calcium Pro Test Kit. While I’m a fan of the Hanna Checker Series it has too much room for user error to produce the most accurate results. You’ll need to match colors to confirm your current calcium levels but they’re easy to read.

Hanna Alkalinity Checker

Alkalinity Test Kit

The Hanna Alkalinity Checker is the best test kit for testing alkalinity levels in your reef aquarium. It’s straightforward to use as well as very accurate. It does have a higher initial cost, but over time the price drops compared to other options if you purchase reagent refills.

Aquaforest Magnesium

Magnesium Test Kit

The Aquaforest Magnesium Test Kit is considered the best. It’s accurate and very consistent. It’s easy to use so that you’re not likely to make errors in the testing process that can cause an invalid reading. Not only that, but it’s inexpensive compared to the other options on the market.

Dosing Calcium In A Reef Tank

Ideal calcium level

  • Minimum Calcium Level 380 ppm
  • Maximum Calcium Level 450 ppm
  • Target Calcium Level 400 ppm

How to test for calcium

There are several test kits on the market for testing calcium. I like the Hanna Checker Calcium Test Kit for their digital readout. It removes the need to try to match colors on a chart. That said, it isn’t the most accurate test kit for calcium. If you want excellent accuracy, I highly recommend the Red Sea Calcium Pro Test Kit. However, if a ballpark number is good enough for you and a digital readout is appealing, try out the Hanna Checker.

How fast can you raise calcium?

Any more than 100 ppm/day is too fast. Consistency of water parameters is critical, so prolonged changes are best to keep calcium levels rising too quickly.

Is too much calcium bad for a reef tank?

Yes. When calcium levels rise above 500 ppm, alkalinity will begin to fall. Therefore, maintaining calcium no higher than 450 ppm will provide all the calcium that stony corals and coralline algae need to grow while not being so high as to make maintaining proper alkalinity levels difficult.

Dosing Alkalinity In A Reef Tank

Ideal alkalinity level

  • Minimum Alkalinity Level 7 dKH
  • Maximum Alkalinity Level 9 dKH
  • Target Alkalinity Level 12 dKH

How to test for alkalinity

The Hanna Alkalinity Checker is the best test kit for testing alkalinity levels in your reef aquarium. It’s straightforward to use as well as very accurate. It does have a higher initial cost, but over time the price drops compared to other options if you purchase reagent refills.

How fast can you raise alkalinity?

No more than 1 dKH per day is recommended to prevent stressing corals. It’s best to make significant alkalinity changes with baking soda instead of soda ash. Baking soda should have no effect on pH, while soda ash will raise pH.

Is high alkalinity bad for a reef tank?

Higher levels of alkalinity (10-12 dKH) can promote coral and coralline algae growth, but levels higher than 10-12 dKH will start to begin causing calcium to precipitate out of the water and cause calcium levels to rapidly drop. Therefore, maintaining alkalinity to 12 dKH or below is crucial to healthy saltwater parameters for stony coral growth.

Dosing Magnesium In A Reef Tank

Ideal magnesium level for a reef tank

  • Minimum Magnesium Level 1200 ppm
  • Maximum Magnesium Level 1350 ppm
  • Target Magnesium Level 1300 ppm

How to test for magnesium

The Aquaforest Magnesium Test Kit is considered the best. It’s accurate and very consistent. By consistent, I mean that it’s easy to use so that you’re not likely to make errors in the testing process that can cause an invalid reading. Not only that, but it’s inexpensive compared to the other options on the market.

How fast can you raise magnesium?

100 ppm per day is recommended. Randy Holmes-Farley over at states that concerns with raising magnesium aren’t with the magnesium itself but with the potential impurities that the dosing agent might contain.

Is high magnesium bad in a reef tank?

Higher magnesium levels beyond the typical 1350 ppm maximum are generally okay. 1500 ppm to 2000 ppm should not cause any problems except with the possibility of harming snails. Higher than normal magnesium levels are sometimes used to combat algae problems or even some fish diseases. Magnesium levels beyond 2000 ppm are not recommended.

Dosing Trace Elements In A Reef Tank

Supplementing minor elements should be done following the guidance of the manufacturer of the trace element dosing supplement. Trace element supplements are usually part of a more comprehensive supplement solution, such as that from Triton Core7 or Brightwell Aquatics Reef Code A&B. A proper system will give you critical guidance on how much to supplement when it comes to minor elements. Or they will combine the typical trace element proportions into some of their other supplements.

Since it’s difficult or nearly impossible to test for specific minor elements aside from ICP testing, it’s best to follow an established program from a manufacturer and follow it up with occasional ICP testing.

Do Water Changes Replace Trace Elements?

Water changes, when performed using a high-quality salt mix, replenish minor elements adequately for most saltwater aquarium and coral needs. The only time you should consider dosing minor elements is if you are trying to grow SPS corals. Small Polyp Stony corals require more calcium and alkalinity as well as magnesium and minor elements.

If you’re not growing SPS corals, dosing minor elements likely won’t make much of a difference and will just add a lot of extra maintenance and expense.

Does a Protein Skimmer Remove Trace Elements?

Yes. There are some elements that a protein skimmer will pull out. This isn’t necessarily a reason to not use a protein skimmer, however. You may want to turn your skimmer off temporarily if you’re manually dosing to allow the minor elements supplement time to dilute, but honestly, this is probably unnecessary.

Periodic ICP testing can give you better insight into the typical levels in your reef aquarium water, and you can use that insight to adjust as necessary.

Best Trace Element Supplement for Reef Tanks

When it comes specifically to trace element supplements, many aquarists swear by Red Sea Coral Colors. Although it is designed to be dosed with the Red Sea Foundation A, which is their calcium supplement. For every 10 ml of Foundation A, you dose 1 ml of each of the minor elements A, B, C, and D.

When it comes to dosing minor elements, it’s best to work with a system that works together. Triton Core7 being the most comprehensive. Tropic Marin All-For-Reef being probably the most hands-off approach.

Can You Overdose Trace Elements in a Reef Tank?

You certainly can. Most trace element supplements are a bit of a black box and more or less impossible to test for unless you’re doing ICP testing. Following the Triton Core7 process is best for people that want to keep a closer eye on all of the various element levels in your tank.

If you accidentally dosed too much of a trace element supplement, the best solution is to immediately do a significant water change to dilute the elements. You’re probably okay in most cases but doing a considerable water change is wise.

Reef Tank ICP Testing

Inductively Coupled Plasma (ICP) analysis is a lab method of testing calcium and alkalinity, plus other elements. It replaces at-home testing of these elements for a more accurate, reliable, and thorough report of all elements found in your aquarium seawater.

For hardcore SPS coral tanks, ICP testing is the best method of managing these elements in your aquarium reliably and accurately.

Triton’s Core7 supplement program relies heavily on ICP testing, and their labs perform the suggested regular testing and indicate what ranges various elements should be within and provide products to specifically address those individual elements.

Most other dosing supplement programs simply provide ballpark dosing, which is helpful for most even if it isn’t as accurate as more advanced solutions like that from Triton.

Can you keep SPS without dosing?

It may be possible to keep 1 or 2 SPS corals without dosing. Still, eventually, as they grow larger, even 1 or 2 SPS will begin to use up the available calcium and alkalinity and magnesium, and other minor elements that regularly get replenished with weekly water changes.

Do LPS corals need dosing?

Generally speaking, LPS corals don’t need dosing to thrive. Regular water changes with a premium salt mix are enough to keep up with their element needs. It may be possible that some heavy LPS tanks could benefit from dosing, though.

If you think that you might fall into this category, you should begin testing calcium, alkalinity, and magnesium regularly to ensure they are maintained in the proper range. If you see an issue, you can then consider dosing to keep elements in check.

When to start dosing a reef tank

You should consider beginning to dose supplemental calcium, alkalinity, magnesium, as well as minor elements when your reef tank reaches 18 months. At this point, SPS and other more demanding corals will begin to use more of these elements than can be replenished by typical weekly water changes. Water changes with a quality salt mix will be sufficient to get your aquarium going but not enough for the long-term health of SPS corals.

How often do you manually dose a reef tank?

How often you supplement various elements will vary significantly from one tank to the next, so there isn’t one set recommendation that can be given regarding how often to dose.

You can test your parameters daily to get a feel for what is happening in your tank. By keeping your finger on the pulse of your water quality daily for some time, you’ll get to know which elements get depleted most quickly and by how much.

Once you grasp the unique needs of your corals, you can begin to formulate your own manual dosing schedule.

Manual Dosing Schedule

Once you’ve gotten more in tune with the ebb and flow of your water parameters, you can begin to establish a schedule that allows you to supplement regularly without daily testing. You can reduce testing down to weekly or even less depending on your comfort level and the coloration, growth, and general health of your corals.

You’ll find that different elements are absorbed and consumed by corals at differing rates. An example manual dosing schedule might look something like this:

  • Alkalinity – Daily
  • Calcium – Weekly
  • Magnesium – Monthly

This is just an example to give you a rough idea of what you can expect from each of the 3 main elements.

What is a dosing pump?

A dosing pump is a small doser that is designed to dose a consistent rate of liquid. For instance, a doser may be designed to dose exactly 1 ml per minute. If you need to dose 3 ml of an element daily, you will set it up to run for 3 minutes each day. You might break this up over a day to dilute the dosage and keep water parameters more stable.

Simply pumps may require a controller to turn them on and off at certain times to measure the dosage they output into your tank. More advanced pumps will have a controller built-in and can be programmed to dispense a certain amount over some time.

Advanced dosers often come in a 4-doser configuration. It is common to need to supplement calcium and alkalinity as well as magnesium and other minor elements. Each of these requires an individual doser. Purchasing one unit that can be programmed to supplement all four of these liquids is ideal.

Are dose pumps necessary?

Dose pumps aren’t necessary, but they are highly recommended. Manual dosing can be forgotten or inconvenient when it needs to be done daily. This can be more challenging when you need to leave your aquarium unattended for a couple of days unexpectedly.

Dosers also have the advantage of dosing amounts of elements over time. This is preferred to dumping the entire dose into the aquarium all at once. This has the benefit of keeping parameters much more stable. Stability is one of the most critical aspects of successfully maintaining corals.

How to set up and use a dosing pump?

Here are the critical steps for setting up and using a doser:

  • Start by getting to know the needs of your corals by measuring alkalinity, calcium, and magnesium daily
  • Determine how much you need to dose of each element and how frequently
  • Place the intake hose into a container of the desired element to supplement
  • Place the output hose into your display aquarium or sump
  • Set up the doser to run for the duration required to dose the necessary amount
  • Set up the pump to repeat this for the interval of the supplement necessary to continually maintain the element over time based on your previously measured observations
  • If possible, alternate the doser on and off over the period between dose intervals to spread the dosage out over a longer time to keep water parameters more stable
  • Test water parameters frequently during the initial runs of the doser to ensure everything is working as intended
  • Continue to monitor water parameters over time and adjust dosage amounts to account for fluctuations in element needs of the corals as they grow

Where should a dose pump be placed?

Like most aquarium equipment, you’ll want to place your dose pumps near your sump hidden within the stand.

Bottles of dosing elements should be lower than the outlet tube end coming from the doser. This will ensure a siphon won’t be created and overdose element into your aquarium.

Outlet tub should be placed just above water level with a holder to ensure they don’t drop into the water itself. This will prevent a back-siphon of aquarium water into your dosing containers.

The outlet of your doser should be placed in the return pump chamber of your sump. If your dosing directly into your display tank, it should be near a powerhead. The idea here is to add supplement to an area that will mix the solution into the aquarium water well, so there won’t be clouds of solution floating through the water column.

What is the best dose pump for a reef tank?

There are lots of great dosing pumps on the market. A good doser should obviously fit your budget, but ideally, you want it to be a programmable 4-head dos. An all-in-one, 4-head doser will help eliminate human error and make dosing a much more set-it-and-forget-it affair than using individual dosing pumps with timers or potentially manually dosing some elements while automating others.

An excellent track record of reliability is probably the most important thing to look for in a doser. Most dosing pumps will fail in the off position if they do fail, which is ideal. This will prevent a possible overdose of element liquid. Researching anecdotal feedback on reefing forums is a good idea, but we can provide some good suggestions.

Jebao DP-4 Doser

Bargain Option

The Jebao DP-4 is a common choice for a budget 4-head pump. It’s programmable and is reasonably reliable for the price. You’ll want to keep a closer eye on it than some of the more expensive options. If your budget doesn’t allow for anything more, it’s a good choice.

GHL 2.1 SA Doser

Premium Option

A big step up in both quality and cost is the GHL 2.1 SA Pump. This 4-head doser is an excellent piece of equipment and a perfect choice for those that can afford it. In addition, the GHL 2.1 SA is expandable via the GHL 2.1 Slave Unit. It, unfortunately, cost almost as much as the master unit, though.

Bubble Magus BM-T11

Mid-Tier Option

Approaching the quality of the GHL is the Bubble Magus T11. While it’s less expensive than the GHL, it can accomplish this in part by only providing 3 pump heads. It is also expandable via the 4-head T12 slave unit, which is considerably more affordable than the GHL.

Best Dosing Supplements for a Reef Tank

Dosing supplements come in 3 different primary forms:

  • Liquid form is convenient but comes at a cost. The added weight of the liquid form means much higher shipping costs. The benefit is not having to mix it yourself, and you can just drop your doser inlet hoses in the jugs and walk away.
  • Concentrate tries to bridge the gap between liquid and powder. You pay less for shipping but still higher than powder. You technically still have to mix it, though, since it will need to be diluted, and you can have more of a crystallized slurry in the container, which can be a little more challenging to mix sometimes than powder.
  • Powder is obviously the lightest but requires mixing. Powders will also survive shipping much more effortlessly than heavy liquid containers and get beaten up in transit and even rupture. Powders being the most economical choice, are obviously very popular. Most people don’t find mixing to be much of a challenge and worth the tradeoff of convenience for price.
Brightwell Reef Code A&B

Bargain Reef Supplement

A very inexpensive powder system that only provides 2 different containers, although still covering all of the major and minor elements for supporting coral health. Only 2 dosing pumps would be required to automate this solution, and it produces excellent results. Of course, some prefer to know what they’re dosing, which I get, but if you want to be more hands-off on the details, Brightwell’s two-part solution is an excellent product to trust.

Triton Core7

Advanced Reef Supplement

Triton provides a comprehensive set of 4 main supplements that are very effective. They also offer a supplement set specifically for those using a large refugium and not doing water changes, which is fantastic and a huge time saver for maintenance. They also suggest ICP testing and provide guidance on adjusting the dosing of the 4 supplements and providing small bottles of specific supplements to address very unique needs.

Tropic Marin All-For-Reef

All-In-One Reef Supplement

Tropic Marin produces the absolutely amazing All-For-Reef single-part dosing solution. It’s very effective at supporting coral health with a single additive. It’s a liquid product, and this puts it squarely in the most expensive range of dosing supplements. It also includes a measuring pump built into the bottle, making it an excellent option for those who want to dose manually. If you’re going to use a dosing pump, you’ll only need one doser, simplifying your setup.

Calcium Reactor Vs. Dosing

Calcium reactors are an excellent way to replace the need to dose a reef aquarium. Calcium reactors dissolve dead coral and slowly drip it into your tank. Dead coral contains everything that you would typically need to supplement into your reef tank.

Calcium reactors simplify issues around dosing significantly, but the cost can be prohibitive for some. The reactor itself is not terribly expensive but requires a CO2 canister, tuning the release of CO2 into the reactor, and using a doser to drip the melted coral into the tank water. It also requires regularly replacing the canister and some other additional maintenance related to the extra hardware.

Overall, calcium reactors are an excellent alternative to dosing due to their ability to maintain reef tank parameters very steadily. And consistent parameters are more critical than parameters that are simply “within spec.”

Final Thoughts on Dosing Calcium, Alkalinity, and Other Minor Elements

Dosing is definitely for more advanced reefers. LPS and soft corals can get all the calcium and alkalinity, and other minor elements they need from the additives in a premium salt mix used when making saltwater for regular water changes.

Dosing supplements are critical to maintaining SPS corals. They need much higher amounts of these elements not just to thrive but to merely survive. Many SPS can’t live on ingredients in salt mixes alone. The ones that can eventually need the support of additional dosing to continue to live and thrive once they’ve grown a year or so.

Testing magnesium, calcium, and alkalinity often will help you get a feel for how much of these elements your corals are consuming and what kind of dosing program you may want to follow to get the most out of your corals.

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