Coral Nutrition Explained: Reef Energy & Feeding Guide

Seawater is 96% pure H2O with only 3.5% essential elements. Marine aquariums use two salinity scales: specific gravity (1.025-1.026) and parts per thousand (30-35 ppt). Higher salinity increases osmotic pressure, facilitating coral nutrient absorption. Calcium is the fifth most abundant element, with 0.41g per liter at 1.025 density. Three critical parameters require monitoring: calcium, alkalinity (reserve alkalinity), and magnesium. Each has ideal concentrations varying by coral types. Parameters fluctuate due to evaporation, organism consumption, precipitation, and chemical reactions between elements.

Marine aquarium success depends on maintaining proper chemical balance, with salinity at 35 ppt being the foundation that affects all other parameters including calcium, magnesium, and trace elements; the nitrogen cycle requires proper rock selection and adequate circulation to process organic waste, while understanding that different aquariums cycle at different rates and require individualized approaches to achieve stability and balance.

Marine aquarium water chemistry involves understanding ion dynamics, trace element management, and biological interactions. Ion shift occurs when dosing calcium chloride and carbonate, inevitably producing sodium chloride as a byproduct, requiring water removal that removes other essential elements. The microbiome, consisting of microorganisms living on and within corals, is essential for coral health and disease resistance. Contaminants like antimony can enter aquariums primarily from UV sterilization units, particularly Asian-made units that combine pumps and UV functions. pH is critically important because indoor CO2 levels (1000-2000 ppm) are much higher than outdoor levels (400 ppm), which can lower pH and shift the carbonate system. Maintaining stable, higher pH levels (8.4-8.5) favors carbonate ions essential for coral calcification.

Marine aquarium chemistry requires balancing key parameters including pH (controlled by CO2 levels), calcium, KH (carbonate hardness), and trace elements, where optimal values depend on salinity (typically 35 PSU) and the presence of living rock or corals; nutrient management involves maintaining detectable phosphorus levels through regular dosing while controlling nitrogen compounds through protein skimming, and any system changes (like switching to new supply systems) may cause temporary biological adjustments but typically stabilize quickly.

Marine aquariums require pure reverse osmosis water as a base because tap water contains contaminants like chlorides and heavy metals that harm marine organisms. RO water is essentially pure H2O, providing a clean canvas for adding precisely formulated marine salts. Ocean salinity consists of six major ions: chloride, sodium, sulfate, magnesium, calcium, and potassium. Sodium chloride represents approximately 86% of ocean salinity, while other salts make up about 14%, with trace elements representing only 1%. Marine aquarium salts are formulated with precise percentages of these ions to replicate natural ocean conditions. Each ion serves specific biological functions: magnesium maintains the calcium-carbonate ratio for coral skeleton formation, sulfate supports coral metabolism, and potassium enhances coral coloration. Salinity can be measured using specific gravity (1.024) or PPT (Parts Per Thousand), with PPT being more practical as it directly relates to grams per liter. For example, 35 PPT equals 35 grams of salt per liter, making calculations more intuitive for beginners.

Autotrophic nutrition is when organisms make their own food through photosynthesis (autotrophs/producers like green plants). Heterotrophic nutrition is when organisms depend on other organisms for food (heterotrophs like humans and animals). Heterotrophic nutrition is divided into three types: saprophytic (feeding on dead matter), parasitic (feeding on living hosts), and holozoic (consuming solid/liquid food).

Autotrophic nutrition is a mode of nutrition in which organisms synthesize their own food from simple inorganic substances like water and carbon dioxide in the presence of sunlight and chlorophyll. Heterotrophic nutrition is a mode of nutrition in which organisms cannot synthesize their own food and depend on other organisms for their food. Organisms with autotrophic nutrition are called autotrophs (like green plants and some bacteria), while organisms with heterotrophic nutrition are called heterotrophs (like animals and fungi).

Autotrophic nutrition is the ability to make one's own food. Green plants, some bacteria, and algae are autotrophs. They use sunlight, carbon dioxide, water, and chlorophyll to synthesize their own food through photosynthesis. Heterotrophic nutrition is the ability to obtain food from external sources. Animals, fungi, and humans are heterotrophs. They depend on plants or other animals for food because they cannot synthesize their own food. Heterotrophic nutrition is divided into three types: (1) Holozoic nutrition - ingesting food through mouth, then digesting it internally (humans, animals, amoeba), (2) Saprophytic nutrition - absorbing nutrients from dead and decaying organic matter (fungi, yeast), and (3) Parasitic nutrition - obtaining nutrients from a living host without killing it (tapeworms, lice, parasites).

Autotrophic nutrition is the mode where organisms can make their own food. The term 'auto' means self, and 'trophic' means nutrition. Autotrophs are also called producers because they form the first level of the food chain. Heterotrophic nutrition is the mode where organisms depend on others for food. The term 'hetero' means other. Heterotrophs cannot make their own food and must consume other organisms or organic matter to obtain energy.

Autotrophic nutrition is the process by which organisms manufacture their own food through photosynthesis or chemosynthesis. Green plants are the primary examples, along with some bacteria. Heterotrophic nutrition is the type where organisms cannot manufacture their own food and must depend on other organisms. Heterotrophic organisms depend on autotrophic organisms for their food supply. Examples include fungi, most bacteria, and animals that feed on plants.

This section covers the nitrogen cycle, one of the most complex biogeochemical cycles. Atmospheric nitrogen (78% of atmosphere) cannot be used directly by most organisms. Nitrogen-fixing bacteria convert atmospheric nitrogen to forms plants can use. Plants absorb nitrogen as nitrates or ammonium. Animals obtain nitrogen by eating plants. Decomposers return nitrogen to soil as ammonium. Nitrification converts ammonium to nitrite and then nitrate. Denitrification converts nitrate back to atmospheric nitrogen. Plants can only absorb nitrogen as nitrate or ammonium, not as atmospheric nitrogen. Understanding nutrient cycles is essential for comprehending ecosystem functioning and environmental science.

The nitrogen cycle shows how nitrogen moves through ecosystems: atmospheric nitrogen is converted by bacteria into nitrates for plants; plants are eaten by animals; animals excrete nitrogen compounds; these return to soil and eventually back to the atmosphere. Lightning can also fix nitrogen. This cycle ensures nitrogen availability for all living organisms. Similar cycles exist for carbon and phosphorus.

The nitrogen cycle describes how nitrogen moves through the atmosphere, living organisms, and soil. Atmospheric nitrogen (about 78%) enters ecosystems through physical processes (lightning) and biological processes (bacteria, cyanobacteria/blue-green algae). Plants absorb nitrogen for amino acid, protein, and vitamin synthesis. When plants and animals die, decomposers break down organic nitrogen and return it to the soil. Plants then absorb this nitrogen again, continuing the cycle. This recycling ensures nitrogen availability for all organisms.

Nutrient cycles are the movement of essential elements (carbon, nitrogen, water, sulfur) between environment and organisms. The carbon cycle involves photosynthesis removing CO2, burning fuel and volcanic eruptions releasing it, and decomposition returning it. The water cycle includes evaporation, transpiration, condensation, precipitation, infiltration, and runoff, distributing fresh water and regulating climate. The nitrogen cycle is complex: N2 gas (78% of air) cannot be directly used; nitrogen fixation converts it to ammonia via lightning or bacteria (Rhizobium, Azotobacter, Clostridium, Cyanobacteria); nitrification converts ammonia to nitrites then nitrates via Nitrosomonas and Nitrobacter; assimilation allows plants to use nitrates for proteins; ammonification breaks down organic matter via decomposers; denitrification returns nitrogen to atmosphere.

Nitrogen forms 78% of the atmosphere and is essential for proteins and nucleic acids. The nitrogen cycle involves circulation of nitrogen gas into different compounds through biotic and abiotic processes. Key processes include: (1) Nitrogen fixation - conversion of nitrogen into nitrates and nitrites through atmospheric, industrial, and biological processes, (2) Ammonia release - through decomposition of dead bodies and excretory wastes, (3) Nitrification - conversion of ammonia into nitrite and then nitrate, (4) Denitrification - conversion of nitrogen compounds into gaseous nitrogen. All organisms participate in the nitrogen cycle. The carbon cycle is particularly effective in temperate regions. Despite constant carbon content on Earth, rising CO2 levels cause temperature increases. The equilibrium of oxygen and CO2 gases is maintained by plants.