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Best Water Parameters for Reef Tanks
Last updated on November 17th, 2023
What are the best water parameters for a reef tank?
This article will focus on finding the ideal parameters for any reef aquarium, focusing not only on the value itself, but the swing that is considered acceptable for these parameters as well. Though much of this, especially Alkalinity, Calcium, and Magnesium apply only to reef aquariums, applying the other parameter values to a fish only tank will help to keep your aquarium happy and healthy.
Best Reef Aquarium Temperature
There is a wide variety in opinion about the "best" temperature for reef aquariums. There have been studies showing different coral and fish living in environments from 60 degrees all the way up to 95 degrees. Even though, we can see this behavior in nature, it is uncommon to keep a home aquarium in this range. This is because most coral or fish from high and low ends of this range will likely not thrive in the opposite end of the range. An example is how cold water coral found in the 60 degree waters will not take well, at least not immediately, to 90 degree water. In order to best keep a wide variety of fish and coral, we generally lean near the middle point of 77 to 80 degrees Fahrenheit.
When it comes to reef aquarium temperature, though the commonly accepted range is roughly 77-80 degrees Fahrenheit. If you live in a colder climate, like the Midwestern States (i.e. Wisconsin) you may want to choose the higher end of this range to help offset the cold. Inversely, in warm climates you may want to try and maintain the lower end of the acceptable range.
Though this range of 77-80 degrees Fahrenheit is considered acceptable, if you stray from this a little, most reef inhabitants will adapt as long as the changes are made slowly. Despite this range where coral, fish, and invertebrates may adapt, reef aquariums are more sensitive to swings in temperature than the exact number itself. When setting up temperature control for your reef aquarium, it is best to keep the temperature stable, within 1 degree Fahrenheit of the temperature you set. You can maintain this temperature control through the use of a Aquarium Temperature Controller.
Learn more about Heaters and Temperature Control in the article: Saltwater Aquarium Heater Guide.
Best Reef Aquarium Salinity
1.024 – 1.025 (32 – 33 ppt) The next most important reef parameter is salinity. The best salinity range for a reef aquarium is 1.024-1.025, or 32-33 ppt. The key methods to maintaining this salinity level are to make sure to mix salt water to the correct levels before a water change, and to utilize an Auto Top Off (ATO) which adds fresh water back to the aquarium as the water evaporates.
Learn more about Auto Top offs in the article: Saltwater Aquarium ATO Guide.
Best Reef Aquarium Alkalinity
Alkalinity, the first of the big three coral growth parameters, has an accepted range between 8-12 dKh. This value should be maintained within 0.5 dKh of the desired value. Some coral can be especially sensitive to large changes over a day's time and therefore alkalinity needs to be maintained quite tightly. Ideally, you will want to dose alkalinity buffer supplements using an Automatic Dosing pump.
Learn more about Alkalinity, Calcium, and Magnesium (The Big Three) in the article: Understanding and Balancing Alkalinity, Calcium, and Magnesium in Reef Aquariums.
Best Reef Aquarium Calcium
400-450 The ideal range for Calcium in reef aquariums is from 400-450 ppm. As the second of the "Big Three" parameters for coral growth, you should monitor this closely, but not with as much exactness as alkalinity. As long as the calcium needed by the coral is present, the coral will generally be happy. The key is that calcium and alkalinity go hand in hand and need to remain balanced. Therefore, you should use an Automatic Dosing pump to keep these values dosed equally.
Learn more about Alkalinity, Calcium, and Magnesium (The Big Three) in the article: Understanding and Balancing Alkalinity, Calcium, and Magnesium in Reef Aquariums.
Best Reef Aquarium Magnesium
Magnesium, the final of the "Big Three", has an acceptable range between 1250-1400 ppm. Though not as critical to maintain as alkalinity and calcium, magnesium plays an important role in coral growth. Magnesium is the parameter that helps coral absorb the alkalinity and calcium needed to grow.
Learn more about Alkalinity, Calcium, and Magnesium (The Big Three) in the article: Understanding and Balancing Alkalinity, Calcium, and Magnesium in Reef Aquariums.
Best Reef Aquarium Nitrates
Until recently, nitrates had always been idea to maintain as low as possible. Recent studies are finding that coral grow and color better with the presence of a small amount of nitrate available. The key to this is that there is very little benefit unless you are keeping SPS corals, in which case you will want between 1-5 ppm nitrates available within your reef aquarium. Since nitrates often come from food and overfeeding, it can be difficult to maintain this value. For this reason, many aquarists that are trying to optimize SPS coral coloration are moving toward maintaining their nitrates at 0ppm, and then add dosing nitrates in a controlled manner. This allows exact values to be maintained.
Best Reef Aquarium Phosphates
Similar to nitrates, phosphates are usually kept as low as possible in the reef aquarium. SPS corals, such as acropora, have been found to have better growth and coloration when there is some amount of phosphate available within the aquarium. The accepted amount of phosphates can be found using the Redfield Ratio. The Redfield Ratio is the ratio of nitrates to phosphates found within the ocean. Though this ratio is ideally utilized for algae growth, it will also provide a familiar nitrate to phosphate level that the coral are adapted to.
The Redfield Ratio indicates that for every 16ppm of nitrate, there will ideally be 1ppm of phosphate. With this ratio in mind, if there is 1ppm Nitrate, there should be roughly 0.0625ppm phosphate. With this, to determine how much phosphate you should have in your aquarium, simply take your current nitrate level and divide it by 16. Like nitrates, since phosphates often come from food and overfeeding, it can be difficult to maintain this value. For this reason, many aquarists that are trying to optimize SPS coral coloration are moving toward maintaining their phosphates at 0ppm, and then add dosing phosphates in a controlled manner. This allows exact values to be maintained.
Best Reef Aquarium Ammonia and Nitrite
For good measure, and completeness sake, I wanted to mention Ammonia and Nitrites. These parameters should ALWAYS be kept at 0. These parameters are toxic to all aquarium life and can quickly kill off an entire tank. Ensure your aquarium is properly cycled before adding life and be patient and add life slowly in order to prevent spikes in these parameters.
Learn more about the Nitrogen Cycle in the article: How to Cycle a Saltwater Fish Tank.
Minor and Trace Elements
Though these are not often measured, and should be the last of your concerns when determining the ideal values for a reef aquarium, I felt like I should comment on these to have a complete resource for you, the readers. Below are the target values for the following trace and minor elements. Please note, you should not try to worry about these values until you are working with a stable reef aquarium for at least a year and know what you are adding, as many supplements have added phosphates and though large amounts of these parameters may not have a major negative effect, the added phosphates may.
- Potassium - 0.3953g/kg
- Bromide --- 0.0663g/kg
- Boron ----- 0.0044g/kg
- Strontium - 0.0079g/kg
- Fluoride -- 0.0013g/kg
Recommended Aquarium Test Kits
To lead you on the right path, below is a list of my preferred test kits.
- Hanna Checker - Alkalinity
- Hanna Checker - Calcium
- Red Sea Test Kits
- Red Sea Reef Foundation Pro Ca/Alk/Mg Multi Test Kit
- Red Sea Alkalinity Pro Test Kit
- Red Sea Calcium/Ca Pro Test Kit
- Red Sea Magnesium Pro Test Kit
Conclusion
If this article was helpful to you, please share it and help someone else that is looking for the best saltwater aquarium parameter levels for their reef tank!
About the Author
John Krenzer
John is a Software Engineer with a passion for saltwater aquariums, as well as the founder and president of Reef Stable. He started in the aquarium hobby as a child with a 20 gallon freshwater aquarium. His interest in aquarium life grew and in 2008, John set up his first saltwater aquarium.
Today, John maintains an over 300 gallon reef tank system, consisting of a 120g reef and a 210g reef. These large tanks are contained within the same system, sharing a sump as a means to reduce total maintenance and increase total water volume.
John writes articles for the blog as a means to learn about more reef aquarium topics. These articles act as a reference for the readers as well as himself. John updates these articles frequently to provide additional information or make corrections as new information becomes available.
If you would like to request an article, tank tour article, or to collaborate, let me know via the Contact Me Page!
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