Glossary: P

PAR

Photosynthetically Active Radiation. Wavelengths of light that can be absorbed by chlorophyll or other light harvesting pigments.

Parameter

A particular physical, chemical, or biological property that is being measured.

Parasite

An organism that feeds on the tissues of another organism. Parasites are one of the major causes of disease in aquarium fishes.

Pathogenesis

Origin of a disease

PC

PowerCompact fluorescent lighting

pH

Provides a measure on a scale from 0 to 14 of the acidity or alkalinity of a solution where 7 is neutral and <7 is acidic and >7 is basic; concentration of hydrogen ions.

PH

See Powerhead

Phosphate

A nutrient that can case uncontrolled growth of algae in the aquarium. It can also toxic in high concentrations and must be kept to a minimum in reef aquariums. Phosphate can be easily removed by a number of commercially available filter medias.

Photoperiod

The length of time your aquarium lights are turned on.

Pico Reef

A small reef aquarium, generally 5 gallons or less. Also known as picoreef or pico-reef.

Plankton

The passively floating or weakly motile aquatic plants (phytoplankton) and animals (zooplankton).

Plug

See Frag Plug

PM

Private message (forum lingo)

Polyp

An individual of a solitary coral or one member of a coral colony.

Powerhead

A small submersible pump commonly used inside an aquarium to provide additional water movement. Several powerheads can be used in conjunction with a controller unit to simulate natural wave actions.

PPM

Parts Per Million

Protein Skimmer

This mechanical filter, also called a foam fractionator, sends many small bubbles through a column of water to separate dissolved organic compounds from the water. They come in many varieties such as venturi, counter-current, and co-current. They are only effective in salt water. They may be placed in the tank, hung on the side, or placed in a sump.