Posted by Christopher Coomer on 4/14/2025 to

Exploring Strontium: The Versatile Element

Introduction

Everyone knows about the "big three" when it comes to maintaining a healthy reef tank: Calcium, Magnesium, and Alkalinity. However, did you know there's actually a fourth element that should be on this list? It's called Strontium, and it plays a crucial role in the health and growth of your reef tank inhabitants.

Strontium, symbolized as Sr and holding the atomic number 38, is a fascinating element with a rich history and diverse applications. This silvery-white metallic element, often tinged with a pale yellow hue, is highly reactive and forms a dark oxide layer when exposed to air.

Historical Background

Strontium was first discovered in 1787 by William Cruickshank and later isolated by Humphry Davy in 1808. Named after the Scottish village of Strontian, where the mineral strontianite was first found, this element has since become integral to various scientific and industrial fields.

Physical and Chemical Properties

Strontium is part of the alkaline earth metals group and is known for its high reactivity. It has a melting point of 777°C and a boiling point of 1377°C. Strontium's electron configuration is [Kr] 5s², and it typically exhibits oxidation states of +2 and +1.

Applications of Strontium

Pyrotechnics: Strontium salts are used to produce vibrant red flames in fireworks and flares.
Glass and Ceramics: Strontium is used to improve the quality and durability of glass and ceramic products.
Medical Uses: Strontium-89 chloride is used in the treatment of bone pain associated with metastatic cancer. Additionally, strontium ranelate has been studied for its potential benefits in treating osteoporosis.
Electronics: Strontium is used in the production of ferrite magnets and in refining zinc.

Strontium in Reef Tanks

Strontium is an essential trace element in reef tanks, playing a crucial role in the health and growth of corals and other marine organisms. Here's how strontium contributes to a thriving reef environment:

Role in Coral Growth

Strontium is similar to Calcium and is used by corals to build their skeletons. It helps accelerate the growth of corals, particularly stony corals like Acropora species. Strontium is incorporated into the coral's Calcium carbonate skeleton, enhancing its structure and stability. This leads to thicker, sturdier branches and increased basal encrustation, which are vital for the coral's overall health and resilience.

Enhancing Coral Health

Maintaining proper strontium levels in a reef tank can improve coral health by supporting their immune system. Strontium, along with other trace elements, helps corals defend against parasites and diseases, ensuring they remain vibrant and healthy.

Improving Coral Coloration

Strontium can also enhance the coloration of corals. Proper strontium levels contribute to the clarity and intensity of colors, particularly the blue hues in corals. This makes the reef tank visually stunning and more appealing to hobbyists.

Supporting Calcareous Algae

Strontium is beneficial for the growth of calcareous algae, which are important for maintaining the reef's ecosystem. These algae contribute to the overall stability and health of the reef tank by providing essential materials for marine life and helping to maintain the water's pH balance.

Maintaining Strontium Levels

To maintain optimal strontium levels, regular testing and careful adjustments are crucial to avoid imbalances that could harm the tank's inhabitants.

Target Levels for Key Elements

Maintaining stable levels of key elements is crucial for the health of a reef tank. While many reefers find a wide range of acceptable targets, CCREEF does not recommend this broad spectrum. Please view our recommended chart for optimal reef health:

General Guidelines:

Calcium: 400-450 ppm
Alkalinity: 7-11 dKH (125-196 ppm as CaCO3)
Magnesium: 1250-1350 ppm
Strontium: 8-12 ppm

CCREEF Recommended Ranges:

Calcium: 425-450 ppm
Alkalinity: 8.5-9 dKH
Magnesium: 1400-1450 ppm
Strontium: 9-10 ppm

To help control any swings and maintain a stable reef tank, CCREEF recommends consistent monitoring and adjustments to keep these parameters within the tighter ranges.

Importance of Stability

Stability is key when it comes to maintaining a healthy reef tank. Fluctuations in the levels of Calcium, Alkalinity, Magnesium, and Strontium can lead to stress and health issues for corals and other marine organisms. Consistent monitoring and adjustments are necessary to keep these parameters stable and ensure a thriving reef environment.

Avoid Chasing Numbers

It's important not to chase numbers. Instead, pick a target and keep it there. Constantly adjusting to hit specific numbers can cause swings in water chemistry, which can be detrimental to your reef tank. These swings can lead to:

Coral Death: Sudden changes in water chemistry can kill corals.
Loss of Color: Corals may lose their vibrant colors due to stress.
Lack of Healthy Specimens: Unstable conditions can result in unhealthy corals and other marine life.

Signs of Strontium Deficiency

Strontium deficiency in a reef tank can lead to several noticeable issues, particularly affecting corals and other calcareous organisms. Common signs include:

Stunted Coral Growth: Slower growth rates in corals.
Weak Coral Skeletons: Brittle and more susceptible to damage.
Loss of Color: Diminished vibrant colors, especially blue hues.
Reduced Basal Encrustation: Less encrustation at the coral's base.
Poor Health of Calcareous Algae: Reduced growth and health.

Recommended Testing

I recommend using Fauna Marin Labs for all your testing needs due to their reliable and accurate solutions. While I personally do not use other test kits, many hobbyists have reported positive results with the following brands:

Salifert Strontium Test Kit: Known for its precision and ease of use.
Seachem Reef Status Strontium Test Kit: Provides quick and accurate results in just 10 minutes.
Triton Strontium Test Kit: Offers comprehensive testing for advanced hobbyists.

Chemical Properties of Strontium

Basic Information

Symbol: Sr
Atomic Number: 38
Atomic Mass: 87.62 g/mol
Group: 2 (Alkaline Earth Metals)
Period: 5
Block: s-block
Electron Configuration: [Kr] 5s²

Physical Properties

Appearance: Silvery-white metallic with a pale yellow tint
Density: 2.6 g/cm³ at 20°C
Melting Point: 777°C (1431°F)
Boiling Point: 1377°C (2511°F)
Crystal Structure: Face-centered cubic (fcc)

Chemical Behavior

Strontium is highly reactive, especially with water and air:

Reactivity with Air: Strontium rapidly oxidizes in air, forming a dark oxide layer. This reactivity requires it to be stored under mineral oil or in an inert atmosphere to prevent oxidation.
Reactivity with Water: Strontium reacts vigorously with water to produce strontium hydroxide and hydrogen gas:

Sr (s) + 2H₂O (l) ? Sr(OH)₂ (aq) + H₂ (g)

Reactivity with Acids: Strontium reacts with acids to form strontium salts and release hydrogen gas.

Oxidation States

Strontium typically exhibits an oxidation state of +2, which is common among alkaline earth metals. This +2 state is due to the loss of its two outermost electrons, resulting in a stable electron configuration similar to that of noble gases.

Isotopes

Strontium has several isotopes.

Strontium-84: Stable
Strontium-86: Stable
Strontium-87: Stable
Strontium-88: Stable
Strontium-90: Radioactive, with a half-life of approximately 28.9 years.

Applications in Chemistry

Strontium's chemical properties make it useful in various applications:

Pyrotechnics: Strontium salts are used to produce red flames in fireworks and flares.
Glass and Ceramics: Strontium is used to improve the quality and durability of glass and ceramic products.
Medical Uses: Strontium-89 chloride is used in the treatment of bone pain associated with metastatic cancer.

Strontium's Role in Maintaining Calcium, Alkalinity, and Magnesium Levels

Supporting Calcium Levels

Strontium is chemically similar to Calcium and is often incorporated into the Calcium carbonate skeletons of corals. This incorporation helps maintain the structural integrity of the corals. Strontium also supports the balance of Calcium in the tank, which is crucial for coral growth and health. Proper levels of Strontium can enhance the effectiveness of Calcium supplements, ensuring that corals have the necessary materials to build their skeletons.

Maintaining Alkalinity

Strontium helps stabilize Alkalinity levels in reef tanks. Alkalinity is essential for maintaining the pH balance of the water, which is crucial for the health of corals and other marine organisms. Strontium's presence helps prevent fluctuations in Alkalinity, ensuring a stable environment for reef inhabitants.

Interaction with Magnesium

Magnesium is another important element in reef tanks, and it works in conjunction with Calcium and Alkalinity. Strontium can indirectly support Magnesium levels by helping to stabilize the overall chemical environment of the tank. Maintaining balanced levels of Calcium, Alkalinity, and Magnesium is essential for preventing precipitation and ensuring that corals can efficiently utilize these elements for growth.

Conclusion

Strontium is a remarkable element with a broad spectrum of uses, from dazzling fireworks to crucial medical treatments. Its unique properties and historical significance make it a subject worth exploring and appreciating. In reef tanks, Strontium plays a vital role in maintaining the balance of Calcium, Alkalinity, and Magnesium, ensuring the health and growth of corals and other marine organisms.

This blog was written by Christopher Coomer, owner and operator of CCREEF. CCREEF is dedicated to providing high-quality aqua-cultured corals, fish, and invertebrates, while promoting responsible reef keeping practices. For more insights and updates, visit CCREEF.

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Sources

Fauna Marin: Detailed insights into the importance of strontium in reef aquariums, including its role in coral growth, coloration, and overall health.
Reefpedia: Information on strontium's role in the growth of corals, calcareous algae, and other marine organisms.

CCREEF Exploring Strontium - The Versatile Element