Temperature and Salinity in Marine Aquariums: Relationship and Impact

Introduction

The topics of temperature and salinity are combined in this article because these parameters are closely interconnected. There are many overlapping nuances that link temperature and salinity, with temperature changes directly affecting salinity. These are two fundamental parameters that must be understood for successful marine aquarium keeping.

Relationship Between Temperature and Salinity

Measurement Challenges

Measuring salinity presents certain difficulties because this parameter depends on temperature. Water density (which determines salinity) changes with temperature fluctuations. There are virtually no reliable sensors and solenoids on the market that would automatically account for this factor. Most salinity measuring devices require reading adjustments depending on water temperature.

By standard, salinity should be measured at a temperature of 25°C (77°F). This means that to obtain accurate readings, it is necessary to heat or cool the water sample to this temperature. However, in practice, this is inconvenient, so it's important to understand how temperature affects instrument readings.

Temperature's Effect on Salinity

When water temperature decreases, salinity readings (water density) increase, and vice versa:

• When the temperature drops from 25°C to 20°C (77°F to 68°F), salinity visually increases from 35 ppt to approximately 35.5 ppt

• When temperature rises, salinity readings decrease

This must be taken into account when measuring and adjusting parameters. For example, if you set the salinity to 35 ppt at 25°C (77°F), then at a temperature of 20°C (68°F) it will be approximately 35.5 ppt, and there is no need to lower the salinity to 35 ppt; you simply need to warm the water.

Optimal Temperature for Marine Aquariums

Choosing a Temperature Regime

The temperature in an aquarium should not be chosen randomly but based on several factors:

Ability to maintain stable temperature:

• If you live in a cold climate, it's easier to maintain a lower temperature (23-24°C/73-75°F)

• In hot climates, it may be problematic to maintain a low temperature without cooling

Biological characteristics of inhabitants:

• Many deep-water corals tolerate high temperatures poorly

• Anemones feel better at temperatures of 20-22°C (68-72°F)

• Blastomussa begin to degrade at 26°C (79°F) after several weeks at such a temperature

Impact on biological processes:

• Lower temperature (23°C/73°F) provides more stable biological processes

• At high temperatures, biological processes accelerate, which can lead to sharp changes and instability of macro and microelements due to their accelerated consumption

Recommended Temperature Ranges

• Optimal range: 23-24°C (73-75°F)

• Acceptable maximum: 25°C (77°F)

• For demanding corals: 23°C (73°F)

• For anemones: 22-23°C (72-73°F)

At temperatures above 27°C (81°F), biological processes occur too intensively, which can lead to system instability. On the other hand, too low a temperature can slow down the metabolism of some species to a critical level.

Cooling the Aquarium

Several methods can be used to lower temperature:

Chillers (aquarium coolers):

• Effective, but have a significant drawback - they emit hot air, which can be a problem in a living space

• Require energy consumption and can be noisy

Fans to enhance evaporation:

• Can lower the temperature by 2-3°C (3.6-5.4°F) even if the air temperature in the room is 28°C (82°F)

• Work through the physical effect of evaporation, which removes heat

• Require regular water top-offs due to increased evaporation

The phenomenon of cooling through evaporation may seem paradoxical: a fan blowing 28°C (82°F) air on water of the same temperature can cool it to 26°C (79°F). This happens because during evaporation, molecules with the highest energy leave the water first, taking heat with them.

• Use fans with a metal grid; they cool the air as it passes through the grid

Temperature and Biological Processes

Impact of Temperature Changes

Temperature directly affects the speed of all biological processes in the aquarium:

When temperature increases:

• Coral and other organism metabolism accelerates

• Biofiltration processes speed up

• Consequences of care mistakes appear faster

• Fish become more active and aggressive

When temperature decreases:

• All biological processes slow down

• Nutrient consumption decreases

• Coral growth slows

• Consequences of mistakes manifest more slowly, giving time to correct them

It's important to understand that an unexpected temperature change (e.g., from 23°C to 27°C/73°F to 81°F) may not lead to serious problems immediately, but after some time (approximately 15-30 days) when changes in biological processes accumulate. The same happens when temperature decreases - a system accustomed to high temperature may destabilize when it decreases.

Using Temperature to Manage the System

Temperature can be used as a tool to manage biological processes in the aquarium:

Preparation for moving or rearrangement:

• Gradually lower the temperature 2-3 weeks before the planned event

• Bring the temperature to about 22°C (72°F)

• Maintain this temperature for a week

• After moving/rearrangement, gradually return the temperature to the original over 2-3 weeks

This slows biological processes and reduces stress for inhabitants.

Coral transportation:

• At 19-20°C (66-68°F), corals can withstand transportation for up to two days

• At 25°C (77°F), safe transportation time is reduced to 1.5 days

• In cold water, corals produce fewer waste products and consume fewer resources

When lowering temperature:

• It's also necessary to reduce feeding, as biological processes slow down

• If the previous feeding regime is maintained, ORP may begin to decrease

Relationship Between Temperature and Other Parameters

Temperature and Carbonate Hardness (KH)

Temperature affects carbonate hardness through biological processes:

When temperature decreases:

• Biofiltration slows down

• Carbonate consumption by organisms and the biofilter itself decreases

• Carbonate hardness may slightly increase (by about 0.5 units)

• This can lead to a small increase in pH

When temperature increases:

• Corals consume carbonates faster and the nitrogen cycle borrows them (not consumes)

• Carbonate hardness may decrease faster than usual

• Dosing adjustment may be required

Temperature and pH

Although there is no direct connection between temperature and pH, biological processes create an indirect dependency:

• Temperature affects the speed of biological processes

• Biological processes affect carbonate hardness

• Carbonate hardness directly affects pH

Thus, temperature change, through a chain of biological processes, leads to pH change. In an isolated system without biological components, such a connection would not be observed.

Temperature and ORP (Oxidation-Reduction Potential)

At low temperatures, ORP may be somewhat lower than at high temperatures. This is not critical because:

• At low temperatures, low ORP values are less critical for the health of inhabitants

• Stability is the key factor

Stability - The Key Factor

The most important rule for temperature and salinity is stability:

Daily temperature fluctuations:

• Rare fluctuations within 3°C (5.4°F) are acceptable (e.g., 23-26°C/73-79°F)

• If the system is accustomed to fluctuations, this does not cause problems

• A sharp transition from a stable temperature to a new stable temperature (e.g., from constant 23°C to constant 26°C/73°F to 79°F) will cause stress and accelerate biological processes

When changing temperature:

• Changes should be gradual (weeks, not days)

• Feeding and additive dosing need to be adjusted

• The system's reaction should be carefully observed

When measuring salinity:

• Consider water temperature during measurement

• Don't try to constantly maintain the same instrument readings at different temperatures

• Set salinity corresponding to your chosen temperature and stick to it

Recommendations for Parameter Selection

For most marine aquariums, it is recommended:

For temperature:

• Choose the optimal temperature for you (23°C/73°F is recommended)

• Ensure the ability to maintain it stably

• Consider the characteristics of the species being kept

For salinity:

• At 23°C (73°F), optimal salinity is about 36 ppt

• At 25°C (77°F) - about 35 ppt

• At other temperatures, adjust accordingly

General rule:

• Choose parameters that you can stably maintain

• Don't try to constantly adjust to instrument readings

• Trust your instruments, but understand their limitations and features

• If the system is thriving but the instrument shows problems - recheck the parameters taking into account temperature and other factors

Conclusion

Temperature and salinity are fundamental parameters of a marine aquarium that require understanding of their interrelationship and influence on biological processes. The correct choice of these parameters and, even more importantly, their stable maintenance are the foundation of successful marine aquarium keeping.

Stability is always more important than ideal values. Even if your parameters differ slightly from the recommended ones but remain stable, the system can function successfully. Sharp changes, even within the recommended values, can cause stress and problems.

Remember that parameters do not exist in isolation - temperature change affects salinity, carbonate hardness, pH, biological processes, and animal nutrition. Understanding these interrelationships will help avoid many problems and create a stable and thriving ecosystem.

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