Autotrophic feeding refers to the way many corals generate energy internally through photosynthesis, using the zooxanthellae living in their tissue rather than capturing external food. This process allows light-dependent corals to meet much of their energy needs directly from the tank’s lighting conditions.

A hydrometer is a simple, inexpensive tool used to measure a saltwater tank’s specific gravity, one way of estimating salinity. While easy to use, it’s generally considered less accurate than a refractometer or digital salinity meter.

Detritus is the accumulated organic debris in a reef tank, including uneaten food, waste, and decaying matter. While a normal part of any system, excess detritus can degrade water quality and fuel nuisance algae if not regularly managed.

Aragonite is a crystalline form of calcium carbonate and the primary material that makes up coral skeletons, reef sand, and live rock. As corals grow, they continuously deposit aragonite, making it one of the fundamental building materials behind a healthy, structurally sound reef.

Carbonate is an ion that, together with bicarbonate, makes up a reef aquarium’s alkalinity. It’s the form corals directly combine with calcium to build their calcium carbonate skeletons, making it central to both water chemistry stability and coral growth.

Nitrite is the second compound produced during the nitrogen cycle, forming as bacteria convert ammonia and remaining highly toxic to most reef organisms. Its presence typically signals an aquarium is still in the process of cycling.

Heavy metals are dense metallic elements, such as copper, lead, or mercury, that can be toxic to reef tank livestock even at very low concentrations. They typically enter a system through contaminated source water, equipment, or accidental exposure.

A deep sand bed is a thick layer of fine sand, typically several inches or more, used to support anaerobic bacteria that process nitrate through denitrification. It offers natural nutrient export alongside its role as habitat for burrowing organisms.

Growth limitation occurs when a coral’s growth rate is restricted by a lack of a specific necessary element or condition, even when other parameters are adequate. Identifying the limiting factor is key to resolving unexpectedly slow coral growth.

Iodine is a trace element that supports certain coral pigmentation processes and plays a role in some invertebrate molting cycles. It’s commonly dosed in reef tanks, though it requires careful, conservative supplementation to avoid overshooting safe levels.

A bacterial bloom is a sudden spike in free-floating bacteria that turns aquarium water cloudy or milky white. Often triggered by excess organic waste, overfeeding, or the addition of bacterial supplements, blooms are usually temporary but signal that the tank’s biological balance is being tested.

Nutrient availability refers to how accessible dissolved nutrients like nitrate and phosphate are to the organisms that consume them within a reef tank. It influences both coral growth and the likelihood of unwanted algae growth.

Digital testers are electronic devices that measure water parameters like salinity, pH, or ORP using probes and sensors rather than manual color-matching or titration. They offer speed and precision, though most still require periodic calibration to stay accurate.

ICP-OES, short for inductively coupled plasma optical emission spectrometry, is the specific laboratory technology most commonly used to perform ICP testing. It measures elemental concentrations by analyzing light emitted from an ionized sample.

Strontium is a minor element found in natural seawater that plays a supporting role in coral skeletal formation alongside calcium. It’s occasionally supplemented in more advanced dosing routines, particularly for fast-growing SPS systems.

Chaetomorpha is a species of macroalgae commonly grown in reef aquarium refugiums to absorb excess nutrients like nitrate and phosphate. Its dense, tangled growth habit makes it easy to maintain and harvest as part of a natural nutrient export strategy.

The nitrogen cycle is the biological process by which bacteria convert toxic ammonia into nitrite, then into comparatively stable nitrate. It’s the foundational process every new aquarium must complete before safely supporting livestock.

ICP testing is a laboratory analysis method that measures a wide range of trace and major elements in a water sample with high precision. It’s commonly used by reef keepers to get a comprehensive snapshot of overall water chemistry.

Bacteria are microorganisms that play a foundational role in reef aquarium health, particularly by driving the nitrogen cycle and breaking down organic waste. Beneficial bacteria colonize rock, sand, and filtration media, quietly converting toxic compounds into safer forms and keeping the system biologically stable.

Diatoms are single-celled algae that commonly appear as a brown, dusty film during a new tank’s early weeks, feeding on available silicates. Their bloom-and-fade cycle is a normal part of the tank cycling process rather than a lasting problem.