Trace Elements in Marine Aquarium Keeping and a Comprehensive Guide to ICP Tests

Introduction to ICP Tests

ICP testing (Inductively Coupled Plasma) is one of the options, and perhaps the only accurate method for determining microelements in marine aquarium water. An ICP test gives you a specific picture of the micro-composition of your water and allows you to draw appropriate conclusions.

It's important to understand that with ordinary home tests, you cannot correctly test most microelements. For example, Manganese cannot be determined using ordinary tests. ICP testing provides more accurate readings, but it also has limitations.

For instance, regarding phosphates: after some time following water collection, when you send the sample to another city (which can take a week or more), the phosphate level already changes. In my experience and that of other aquarists, such tests often show incorrect results for phosphates.

For accurate phosphate measurement, it's better to use a photometer (Hanna or Milwaukee). For determining low values (which is important for reef aquariums), use an "ultra low" tester or one for "phosphorus." Multiply the "Phosphorus" meter readings by 0.0031 to get the phosphate value.

Limitations of ICP Tests

ICP tests don't always give a complete picture. They determine only the total amount of a substance, without distinguishing forms. For example, iodine has at least three forms (iodide, iodate, and elemental iodine), but only active elemental iodine is important to us.

The ICP test will show the total iodine content (the entire reserve which doesn't fully affect coral coloration and nutrition), these values may be dangerously high (400-900 μg/L), but the active elemental iodine from this amount may be only 50-90 μg/L, which is normal.

The same applies to other elements, such as Tin. There are organic and inorganic forms. Only the organic form of Tin is biologically active and can be dangerous at levels above 25 μg/L. Therefore, one aquarist may have a Tin level of 50 μg/L and have no problems with corals, while another at a level of 40 μg/L may observe negative effects on corals.

The Influence of Biology on Aquarium Chemistry and Vice Versa

Inorganic elements can transition to organic form through consumption, for example by algae. When algae saturated with chemicals die from any cause, chemical elements from these algae are released in an organic, biologically active form and can cause problems for your corals.

Overview of Microelements and Their Importance

Some elements are critically important, others less significant. A number of elements contained in salt may be considered "chemical waste" — in certain quantities they cause no harm, but offer no particular benefit either.

If an ICP test shows the presence of an element that is not in your salt mix, it's worth finding its source. It's especially important to monitor dynamics — if some element starts to accumulate, you need to find and eliminate the source to avoid negative effects on living organisms.

Critical Considerations

Some elements can stop the entire calcification process and cause increased algae activity. For example, phosphates in large quantities affect ions and stop the calcification process of coral skeletons. At phosphate levels above 0.5 mg/L, the calcification process is practically impossible.

With high phosphate levels, you'll see slight breakdown of rocks, the water acquires a yellowish color, and photosynthetic planarians multiply rapidly.

Categories of Elements by Dosing Necessity

Elements for daily dosing without testing:

• Manganese
• Cobalt
• Chromium
• Iron
• Vanadium

These elements need to be dosed daily without worrying about testing. They are rapidly consumed, and even if an ICP test doesn't show them (which usually happens), that's normal. They are dosed according to water volume, not by the number of corals.

Elements for dosing after ICP testing (corrections):

• Calcium
• Magnesium
• Potassium
• Bromine
• Strontium
• Boron
• Fluorine
• Barium
• Molybdenum
• Nickel
• Zinc
• Tin

General Recommendations

Using a Calcium Reactor

Using a calcium reactor usually minimizes the need for adjustments of many substances, as good calcium reactor media contains all these elements. A calcium reactor is significantly more effective than "Balling" (the method of dosing individual elements).

For aquariums from 300 liters, it's recommended to install a calcium reactor at minimal dosing for stable maintenance of parameters.

What Are Corrections

Corrections are actions after an ICP test when you discover a deficiency of certain substances and add appropriate supplements. For substances that can be measured with ordinary tests (calcium, magnesium, KH), corrections can be made based on home tests. For other elements (boron, fluorine, barium, molybdenum, nickel, zinc), an ICP test is needed.

When making corrections, it's important not to raise parameters all at once, but to do it gradually over several days. After some time, it's recommended to do a new ICP test and make new corrections if necessary.

About Phosphates

If you need to increase phosphate levels, it's better to use spirulina or nori-based foods instead of chemical preparations. This provides a gradual supply of organic phosphate, which is better absorbed by bio-organisms.

By regulating the amount of food, you can control the phosphate level in the water.

Important Cautions

Do not mix complex microelement mixtures with each other in advance. If you store microelements mixed together, this may nullify the effects of both. Chemical processes lead to precipitation of essential elements, and when dosing, there will be no effect.

Even products from the same manufacturer that are theoretically compatible (for example, from the Tropic Marin or Aqua Forest line) may form precipitates when mixed in practice. Use separate doser channels for each preparation.

Detailed Review of Elements and Their Optimal Values

Alkalinity (Carbonate Hardness)

• Target value: 8 ± 0.5 units (range 7.5-8.5)

Magnesium

• Target value: 1350 mg/L
• Actions at level <1250 mg/L: Need to raise, calculated by calculator. Do this gradually, over 2-3 days if the difference is large.
• Actions at level >1400 mg/L: Need to reduce dosage, as light impact on corals will be slightly stronger.
• Features: With high levels of Magnesium, Calcium, and KH, corals receive "overexposure"; with low levels — they look as if they're not getting enough light. This creates an effect as if you're constantly adjusting the brightness of your light fixture.

Sulfur

• Note: If sulfur levels exceed 1000 mg/L, monitor dynamics in subsequent ICP tests.
• Features: Sulfur levels often temporarily increase after correcting magnesium with certain additives, as magnesium mixtures often contain sulfur.
• Recommendations: If an increase in sulfur is noticed after magnesium correction, this is normal. If sulfur increases without apparent reasons, check the salt composition and dependence on water changes.

Calcium

• Target value: 420-440 mg/L (not 450!)
• Actions at level <400 mg/L: Must raise to 420 mg/L.
• Actions at level >440 mg/L: Reduce dosage.
• Observations: At 430-420 mg/L, corals often inflate polyps better than at 450 mg/L and especially at 500 mg/L.
• Effect on corals: With the correct calcium level, coral colors will be more vibrant, and polyp extension better.

Potassium

• Target value: 410 mg/L
• Actions at level <400 mg/L: Need to raise.
• Actions at level >420 mg/L: Better to reduce dosing.
• Actions at level >500 mg/L: Need to do water changes to reduce potassium level to at least below 500 mg/L.
• Effect: Like other macroelements (calcium, magnesium, carbonate hardness), potassium affects how corals perceive light and can affect algae growth.

Bromine

• Target value: 85 mg/L
• Actions at level <65 mg/L: Need to raise.
• Actions at level >100 mg/L: Reduce dosage.
• Sources of elevation: Often released from magnesium media in calcium reactors. If you notice an increase in bromine, check the magnesium media in the reactor.

Strontium

• Target value: 10 mg/L
• Actions at level <4 mg/L: Raise as soon as possible.
• Actions at level 4-6 mg/L: Basically normal, but better to raise above 6 mg/L.
• Actions at level 10-20 mg/L: Need to reduce dosages.
• Actions at level >40 mg/L: Need to do an urgent water change.
• Special cases: With prolonged strontium deficiency (2-5 mg/L), it's recommended to temporarily raise it to 25 mg/L. This is needed to restore coral skeletons, which will actively consume strontium over several months. After this period, you can return the level to 10 mg/L.

Boron

• Target value: 7 mg/L
• Actions at level <3 mg/L: Raise quickly, as the value is critically important.
• Actions at level 4-5 mg/L: Basically normal, but better to raise to 7 mg/L.
• Actions at level >10 mg/L: Need to do a water change to reduce.
• Effect: Boron stabilizes pH levels, making them more stable between day and night periods. With chronic boron deficiency, you may face pH instability and loss of red coloration in corals.

Fluorine

• Target value: 0.5-0.7 mg/L
• Actions at level <1 mg/L: Raise quickly, as starvation is possible.
• Actions at level 1-1.2 mg/L: Basically normal, but better to raise to create a reserve.
• Actions at level 1.8-1.9 mg/L: Reduce dosage.
• Actions at level >2 mg/L: Water change needed to bring fluorine below 2 mg/L.
• Effect: Excess fluorine can cause tissue damage and coral bleaching.

Lithium

• Normal range: 100-400 μg/L
• Actions at level <100 μg/L: Need to raise.
• Actions at level >1000 μg/L: Need to do a water change to bring lithium below 900 μg/L.
• Effect: At levels of 1500μg/L and above, corals begin to pale.
• Features: A 15% water change reduces lithium levels by about 10% from the initial level.
• Contamination sources: Some plastic containers from stores may release lithium.

Silicate (Silicon)

• Normal range: 100-200 μg/L
• Actions when elevated: Check your RO system. Possibly the system is not working correctly, and TDS is above zero.
• Reduction methods: Use products for silicate removal (adsorbents, resins) or, preferably, eliminate the source.
• Effect: Silicates are quickly consumed by algae and other organisms. Excess is food for unwanted algae.
• Contamination sources: Glass, plastic, sand, rocks, ceramics can release silicates, especially in a new aquarium.

Iodine

• Target value: 60-90 μg/L
• Actions at level <20 μg/L: Need to dose daily to raise.
• Actions at level 45-50 μg/L: Basically normal, but better to raise gradually by adding doses.
• Actions at level >90 μg/L: Stop dosing additives for a week.
• Effect: Affects metabolism, enhances blue coloration in corals, improves nutrition and polyp extension.
• Features: Iodine may show high values in ICP tests (300-400 μg/L), but active elemental iodine may be only 90 μg/L. If corals look normal, don't worry about high readings, but stop dosing for a week and test the water again.

Barium

• Target value: 15 μg/L
• Actions at level <6 μg/L: Raise quickly, as this is an important element.
• Actions at level 8-10 μg/L: Basically normal, but better to raise to 15 μg/L.
• Actions at level 20-50 μg/L: Reduce doses and wait for reduction.
• Actions at level >60 μg/L: Urgent water change needed.
• Special cases: If an aquarium has been maintained at low barium levels (2-5 μg/L) for a long time, it's recommended to raise the level to 25 μg/L for several months. Corals will actively consume barium to strengthen their skeleton.
• Importance: Barium is critically important for building coral skeletons and is replenished only through water changes or special additives (such as Tropic Marin K+ Elements or Aqua Forest).

Molybdenum

• Target value: 15 μg/L
• Actions at level <6 μg/L: Raise as soon as possible.
• Actions at level 10-15 μg/L: Basically normal, but better to maintain closer to 15 μg/L.
• Actions at level 20-30 μg/L: Reduce dosage or stop dosing.
• Actions at level >50 μg/L: Water change needed.

Nickel

• Target value: 2.5 μg/L
• Observation: Usually if not dosed, it depletes itself, being consumed by the system.
• Important: Levels of 20-30 μg/L indicate corrosion of equipment in your system, especially if you're not dosing anything.

Zinc

• Target value: 5 μg/L
• Actions at level <1 μg/L: Raise to 5 μg/L.
• Actions at level 1-3 μg/L: Basically normal, but better to raise to 5 μg/L for reserve.
• Actions at level 10-20 μg/L: Reduce dosing.
• Actions at level >40 μg/L: Water change needed.

Tin

• Note at level 30-50 μg/L: Look for what's releasing tin in the aquarium (pumps, plastics, equipment).
• Actions if ICP test detects tin: No need to add, the element is consumable.
• Target dosage: 0.1 μg/L per day for most aquariums.
• Features: Tin can transition from inorganic to organic form and accumulate. ICP tests may show high values, but in organic form it may be normal.
• Recommendations: Better not to overdose in order to understand the true consumption pattern.

Copper

• Normal state: Should not be detected in tests if not dosed.
• Range 0-1 μg/L: Indicates input from food, medications, salt, or aquarium elements.
• Range 1-3 μg/L: Monitor with tests, possible fluorescence disruption.
• Level >3 μg/L: Urgent water change needed to reduce to at least below 3 μg/L, otherwise corals may pale.
• Professional application: Product Spour 2 from Korallen-Zucht for reducing zooxanthellae in corals. Makes them lighter and stimulates growth.

Silver

• Normal: Should not be detected in tests if not dosed.
• If detected: Look for the source (decorations, equipment with silver).
• Application: Only for very experienced aquarists for experimental purposes.

Vanadium

• Target value: 1-2 μg/L
• Dosage: 0.1 μg/L per day for most aquariums.
• Features: Quickly consumed and never determined by tests.
• Effect: Beneficial additive, quickly consumed by corals and other organisms.

Manganese

• Target value: 5 μg/L when measured (usually not detected)
• Dosage: 0.1 μg/L per day (minimum), can be increased twofold for better effect.
• Effect: Enhances metallic shine in coral coloration (a kind of UV protection), improves fluorescence of SPS corals, supports algae growth.
• Accumulation effect: Not manganese itself accumulates, but its effect. Creates a protective film on corals, preventing overexposure.
• Action period: The effect lasts about a week. If dosing is stopped, after 3-4 days corals begin to react to light differently.
• Features: Quickly consumed by algae. After removing part of the algae, manganese consumption changes dramatically.

Chromium

• Dosage: 0.2 μg/L per day is normal for most aquariums.
• Features: In excess, it can transition from organic form to chemically inactive form and accumulate in water.
• Actions if detected by test: Temporarily stop dosing.

Cobalt

• Dosage: 0.1-0.2 μg/L per day for most aquariums.
• Features: Always depletes; if an ICP test shows it, separate dosing is not needed.
• Effect: Has a positive effect on soft corals.
• Note: Excess can suppress fluorescence.

Iron

• Dosage: 0.1 μg/L per day for most aquariums.
• Effect on corals: With overdosing, yellow corals may turn greenish. Reduce the dose with such symptoms.
• Consumption: Quickly consumed by algae, especially algae filters.
• Adaptation: SPS corals adapt to iron within a week. Overdose effects aren't visible immediately but appear after 7-10 days.
• Note: Iron dosing can enhance red color in corals, compensating for a lack of biologically active component.

Rubidium

• Target value: 0.2 mg/L
• Dosage: 0.1 mg/L every 3 months or 0.33 mg/L monthly.
• Features: Decreases very slowly, so correction can be done once every 3 months.
• Benefits: Very useful for mixed reefs, especially for zoanthids, rhodactis, other mushrooms, and soft corals.
• Important to know: Expensive element, rarely included in additives and salt mixes due to cost and limited research.

Aluminum

• Target value: 0-15 μg/L
• Effect: Aluminum in water indicates that something is releasing it (metal parts, food, filters).
• Effect on corals: Negatively affects fluorescence, corals become dull.
• Actions at level <40 μg/L: Basically doesn't harm the aquarium.
• Actions at level >40 μg/L: Water change needed.
• With constant growth: Look for the source in the aquarium or change salt/microelements.

Amino Acids and Special Additives

Amino Acids

Amino acids are only useful when you've already achieved good coral coloration. They can add brightness and clarity to colors, but with poor initial conditions, they may only exacerbate problems (stimulate algae, enhance color loss).

The exception is Acropower. This is not exactly an amino acid, but a growth stimulant (often called a "steroid for corals"). Acropower doesn't enhance coloration but significantly accelerates growth. According to observations, corals can grow 5-10 times faster than normal.

When using Acropower, you need to increase the dosing of all microelements by about 50%, as element consumption also accelerates. Pay special attention to Phosphate, as its sharp decrease can cause coral death due to phosphate shock.

Spour 2 (Korallen-Zucht)

A special copper-based preparation for reducing zooxanthellae in corals. Makes corals lighter and stimulates growth.

• Application: According to instructions, activated carbon must be removed.
• Effect: Occurs maximally after 2 days. After the first dose, corals lighten about 2 times; after the second — even more.
• Note: May negatively affect some organisms (anemones, mushrooms), which may lose color and begin to slowly degrade.

Practical Recommendations and Common Mistakes

Water Changes

Each 15% water change reduces element concentration by about 10% from the initial level. This applies to any element, and remember that new saltwater also contains elements.

Element Interactions

Many elements affect each other. For example, excess potassium, strontium, or magnesium can make corals more sensitive to light burns, even if lighting hasn't changed.

Adaptation Time

Some effects from changing element levels aren't visible immediately:

• Iron: SPS corals adapt over a week
• Manganese: The effect of manganese accumulates over several days, and when dosing stops, lasts about a week
• Iron: Excessive greening of corals may appear 7-10 days after increasing the dose

Microelement Consumption by Algae

Algae, especially macro-algae, actively consume many microelements (iron, manganese). When you remove part of the algae, element consumption changes dramatically. This can lead to their accumulation if you continue dosing the same amounts.

Dosing Microelements

Many elements (manganese, iron, iodine, vanadium, cobalt, chromium) are dosed according to water volume, not the number of corals. Even if you have only a few corals, the dosage remains the same as for an aquarium with many corals of the same volume.

Influence of Microelements on Aquarium Biology

Phosphates

• Critical level: At concentrations above 0.5 mg/L, the calcification process and coral skeleton building practically stops
• Effect on structures: High phosphate levels can cause surface degradation of rocks, which begin to crumble into sand
• Signs: Yellowish water, rocks have a yellow tint, absence of coralline algae and proliferation of photosynthetic planarians.

Iodine

• Effect: Increases intensity of blue color in corals, improves general condition of polyps
• Deficiency: Corals may die from starvation as many biological processes depend on iodine
• Forms: Iodide and iodate gradually transition to elemental iodine, but only elemental iodine is biologically active and only it gives the necessary, visible effects.

Barium

• Importance: Critically necessary for coral skeleton formation
• Deficiency signs: Reef degrades without obvious reasons, despite good indicators of basic parameters
• Feature: Comes only with water changes or special additives

Boron

• Function: Stabilizes pH, reducing fluctuations between day and night
• Deficiency: Can cause constant pH fluctuations that are difficult to explain

Manganese

• Effect: Creates protective "tan" on corals (metallic sheen), protecting from overexposure
• Benefits for SPS: Supports fluorescence and makes polyps more resistant to light
• Effect accumulation: Protective effect persists for about a week after stopping dosing

Iron

• Effect on color: With overdosing, yellow corals may acquire a greenish tint
• Effect on polyps: Can enhance red color in corals with proper dosing
• Adaptation: SPS corals adapt to new iron levels within a week

Rubidium

• Users: Especially useful for mixed reefs with zoanthids, rhodactis, and bonsai
• Reproduction: Accelerates reproduction of soft corals and Zoanthids
• Note: Rarely found in additives due to high cost and limited research

Practical Tips for Correcting Element Levels

Approach to Corrections

1. Never make sharp changes in element levels
2. Raise parameters gradually, over several days
3. After correction, do a new ICP test after 1-2 months
4. Consider element interactions when making corrections

How to Make Water Changes to Reduce Excess Elements

• A 15% water change reduces element concentration by about 10%
• When reducing problematic elements, consider that new saltwater also contains these elements
• For serious excesses (copper, lithium), several water changes may be required

Calcium Reactor vs Balling

A calcium reactor significantly simplifies maintaining many microelements:

• Coral Rubble in the calcium reactor contains most necessary microelements
• The reactor provides stable supply of elements
• With proper setup, it minimizes the need for manual corrections

Balling requires more careful control and often leads to imbalances.

How to Work with ICP Tests

1. Do tests regularly (once every 2-3 months)
2. Pay attention not only to absolute values but also to dynamics
3. If some element constantly rises or falls, look for the cause
4. Consider the limitations of ICP tests (for example, with phosphates)

Special Additives and Their Use

Acropower (Growth Stimulant)

• Effect: Accelerates coral growth 5-10 times
• Application: Start with a dose 10-15% higher than recommended, then adjust
• Important: Increase dosing of all microelements by about 50%
• Signs of action: Noticeably increased consumption of phosphates and other elements

Spour 2 (Korallen-Zucht)

• Purpose: Reduces zooxanthellae in corals
• Application: Remove activated carbon before use
• Result: Corals lighten and begin to grow faster
• Effect: Occurs 1-2 days after application
• Caution: May negatively affect anemones and some soft corals

Cautions About Amino Acids

• Amino acids are useful only after achieving good basic coral coloration
• Under poor conditions, amino acids may stimulate growth of unwanted algae
• Don't use amino acids as a solution for coral color problems

Analysis of Typical Problems and Their Solutions

Problem: Corals Losing Color

Possible causes:

• Iodine deficiency (check level)
• Excess copper (>3 μg/L)
• High aluminum level (>40 μg/L)
• Excess iron (manifests a week after increase)
• Manganese deficiency (reduces light resistance)

Solutions:

• Check and correct levels of corresponding elements
• For excess elements, do water changes
• For deficiencies, add elements gradually

Problem: Corals Stopped Growing

Possible causes:

• Barium deficiency (<6 μg/L)
• High phosphate level (>0.3 mg/L)
• Strontium deficiency (especially prolonged <4 mg/L)
• Calcium/magnesium/carbonate hardness imbalance

Solutions:

• Check barium level, you may need to temporarily raise to 25 μg/L
• Reduce phosphates (adsorbents, less feeding)
• Correct strontium level
• Check and establish proper Ca/Mg/dKH balance

Problem: Sudden Appearance of Algae

Possible causes:

• Elevated silicate level (>200 μg/L)
• Excess iron and manganese
• Reduced consumption after removing part of algae

Solutions:

• Check RO system operation and silicate level
• Temporarily reduce iron and manganese dosage
• After removing algae, reduce dosing of these elements

Problem: Unstable pH

Possible causes:

• Boron deficiency (<3 mg/L)
• Very low carbonate hardness
• Ventilation problems in the room, too much CO2
• Presence of oxidizers in water due to powerful Nitrogen Cycle

Solutions:

• Increase boron level to 7 mg/L
• Stabilize carbonate hardness in the range 7.5-8.5
• Check air circulation, direct the Skimmer air intake tube outside.

Conclusion

Understanding the balance of microelements is key to successful marine reef aquarium keeping. Regular testing with ICP tests, proper dosing, and correction of levels allow you to create optimal conditions for coral growth and coloration.

Remember that an aquarium is a complex biological system where all elements are interconnected. Often, problems that seem inexplicable have a simple cause — an imbalance of macro and microelements.

Patience, attention to detail, and a systematic approach to parameter control will ensure your marine aquarium thrives and remains beautiful for many years.