P - Aquarium Dictionary

Updated August 12, 2019
Author: Mike - FishLore Admin
Social Media: FishLore on Social Media

Aquarium Fish Definition and Glossary

abbreviation for Photosynthetically Active Radiation. It is the amount of light that is available at depth for corals, plants and other photosynthetic organisms. It is important to know how much PAR your light fixture puts out so you can know what types of light demanding corals you can keep and/or where to place them depth wise in your tank. You can measure PAR using a meter:
PAR Meter
PAR Meter on Amazon

Paraguard :
is an aquarium medicine made by Seachem used to treat parasites on fish. Used to eradicate many ectoparasites (ich) and external fungal, bacterial, and viral lesions (fin rot).
Paraguard on Amazon

Parasite :
is an organism that lives on or in another organism and benefits by stealing nutrients at the host organism's expense. Fish can get parasites with the most common being ICH. You can use Paraguard on Amazon to treat parasites in fish.

Parasitism :
a form of symbiosis in which one organism benefits from the association and the other organism is harmed.

PC :
abbreviation for Power Compact and refers to Power Compact fluorescent lights.

Peat Moss :
you can add peat moss to your tank or filter to help create soft, acidic water that is sometimes required to induce spawning for certain fish species. Peat moss contains natural acids and tannins. More:
Peat Moss
Peat Moss on Amazon

Pelagic :
for our purposes, this term is usually used when referring to the breeding styles of many marine species. These species essentially release the fertilized eggs into the open ocean to be carried by the currents. This breeding style can be quite difficult for breeders to successfully raise larvae.

Pennywort :
Hydrocotyle tripartita, is an aquarium foreground plant that is considered easy to grow. More below:
Pennywort on Amazon

PFS - Pool Filter Sand :
is sand that is used in aquariums sometimes because it is cheaper than other types of sand. See:
Pool Filter Sand
Pool Sand on Amazon

pH :
this is a water measurement on a logarithmic scale that will tell you if your water is considered acidic, neutral or alkaline. A pH of 7 is considered "neutral", under 7 is considered "acidic" and over 7 is considered "alkaline". Get a pH test kit to measure the pH of your aquarium:
pH Test Kit on Amazon

Phosban :
is an aquarium product made by the company Two Little Fishies and is used to remove phosphate from aquarium water. These are ferric oxide hydroxide granules with an extremely high capacity for adsorbing phosphate from saltwater and freshwater. Also adsorbs silicate and does not release adsorbed substances. This is best used in a TLF media reactor. Get phosban below:
Phosban on Amazon

Phosguard :
an aquarium product made by Seachem that is used to remove phosphates and silicates from aquarium water. Phosphates and silicates in tank water can lead to nuisance algae blooms. You can run it in a media reactor or place a bag of it in your sump, although you will get much better results running it in a reactor. 100 milliliters treats 60 US gallons. See:
Phosguard on Amazon

Phosphate :
PO4, consists of Phosphorous and Oxygen, is a primary ingredient for algae. Aquarists should try to limit phosphates in the aquarium water to prevent noxious algae blooms. Get a phosphate test kit to test your tank water:
Phosphate Test Kit
PO4 Test Kit on Amazon

PimaFix :
a freshwater and saltwater fish medication made by API and is used to treat fungal and bacterial infections in fish. API claims that it alleviates symptoms like fungus or cotton like growths on fins, mouth and body. Safe to use in reef tanks and will not harm the biological filter. Use 5ml per 10 gallons of aquarium water.
PimaFix on Amazon

Piscinoodinium :
the freshwater version of the parasitic single cell organism in velvet disease.

Pleco :
is a type of freshwater fish. Also known as the Plecostomus. See the Pleco profile page for more information on this species.

Plant Anchors :
Plant anchors are weights used to help keep aquarium plants in place. See more here:
plant anchors
Plant Anchors on Amazon

Plenum :
mostly used only in saltwater aquariums, this is an open space under a deep sand bed that is used to promote biological filtration in the sand bed.

Pothos Plant :
Pothos is a very hardy house plant that is also used in aquariums to help filter the water. Since it isn't a fully aquatic plant (the whole plant should not be submerged in the water), the roots are submerged in the aquarium and help clean the water just like using aquarium plants would, though perhaps does not perform quite as well as using a fully aquatic plant. This concept is similar to using mangroves in saltwater aquariums. More info on pothos:
pothos plant
Pothos Plants on Amazon

Power Compact Light :
is a U shaped fluorescent light that is able to generate more light than standard fluorescent tubes. Power compacts are reported to be more energy efficient while producing more light intensity. They can be a viable alternative for smaller and shallow saltwater reef tanks. They do put off some heat and a fan may be needed. They range anywhere from 9 watts through 96 watts.

Power Filter :
an HOB aquarium filter that performs mechanical filtration, biological filtration and chemical filtration. It performs mechanical filtration by pulling in tank water and forcing it through filter floss. Chemical filtration is accomplished by using activated carbon inside the filter floss. The better power filters also have a course media that the water flows through as it exits the power filter. This course media is a colonizing area for the beneficial bacteria that perform biological filtration. These aquarium filters are very popular because they are inexpensive, easy to maintain and do a decent job. It is important to replace the filter floss (not the bio-filter) when needed to prevent nitrates from accumulating in the filter.
Power Filter
Power Filter on Amazon

power head :
is aquarium equipment that is used to perform water movement inside the aquarium. power heads can be great if you don't want to run plumbing lines to an external water pump. power heads are also sometimes used with a UGF to create a reverse flow undergravel filter. There are some drawbacks to using power heads inside your aquarium. They can add heat and using several can be a problem if tank temperature is staying too high. The water intake strainer needs to be cleaned on a regular basis to perform at peak efficiency and having several in a tank can be a bit distracting and take away from the beauty of a tank (personal opinion of course). For more details on powerheads see:
Powerheads on Amazon

Parts Per Million, is a unit of measurment used in many test kits and is equivalent to mg/L.

Prazipro :
a medication for freshwater, saltwater and pond fish that treats disease conditions such as flukes, flatworm and turbellarians. 5 percent praziquantel by weight.
PraziPro on Amazon

Prime :
an extremely popular water supplement that helps with the slime coat on fish, removes chlorine and chloramine and detoxifies ammonia, nitrite and nitrate. Seachem Prime effectively detoxifies ammonia, nitrite, and heavy metals found in the tap water at typical concentration levels. Use 1 capful (5 mL) of Seachem Prime for each 200 L (50 US gallons) of new or replacement water. For best results, add Seachem Prime to new water first. For exceptionally high chloramine concentrations a double dose may be used safely. For smaller volumes use 2 drops per gallon.
Prime on Amazon

Pristine :
aquarium supplement made by Seachem that contains bacteria that breaks down detritus, excess food and sludge in both freshwater and saltwater aquariums. It is also supposed to reduce excess nutrients (e.g. ammonia, nitrites and nitrates). Used to increase water clarity and better health in your aquarium.
Pristine on Amazon

Protein Skimmer :
a saltwater aquarium filtration device used to remove dissolved organics from the water using a process called foam fractionation. The protein skimmer pulls in water from the fish tank and then agitates it thereby forming tiny microbubbles. These tiny microbubbles attract the dissolved organics on the bubble surface. As these bubbles accumulate they are slowly forced upwards into a skimmer collection cup. Frequent maintenance is vital for the proper operation of a protein skimmer. The collection cup, the riser tube the bubbles travel up through and the water intake into the skimmer should be cleaned frequently to keep the skimmer operating a peak capacity. Protein skimmers help by removing these dissolved organics before they have a chance to turn into nitrates. If these dissolved organics are not removed from the water column they can cause problems such as nuisance algae growth, yellowing of the water, and an overtaxed biological filter.

Protogynous Hermaphrodite :
when a species begins life as a female and changes to a male. Often only a one way change, (i.e they can't change back to female) that can be triggered by the death of the lead male in the harem, the dominant female will turn into a male. The change process can take weeks to months to complete.

Pulsing Xenia :
see Pulsing Xenia for detailed information - a coral with polyps that pulse.

Purigen :
an aquarium product made by Seachem that removes impurities from aquarium water. Purigen controls ammonia, nitrites and nitrates by removing nitrogenous organic waste before it breaks down in the tank. It does have a minimal impact on trace elements. It claims to significantly raise redox. Purigen darkens as it exhausts, and is easily renewed by treating with bleach. Purigen is designed for both marine and freshwater use.
Purigen on Amazon

Poly Vinyl Chloride, is a hard plastic type material used in plumbing aquariums and for routing water throughout multiple systems.

abbreviation for Partial Water Change. More info on aquarium maintenance.

Python Water Changer :
aquarium equipment designed to make it easier and quicker to do partial water changes. Do you hate carrying around those heavy 5 gallon buckets for water changes? If so, the python water changer may be perfect for you. It hooks up to your faucet and will remove old water and then refill with new tap water. You have to treat the water as it is added to your tank with prime or similiar. Make sure the temperature is as close as possible to the tank water too to prevent stressing out the fish!
Python Water Changer
Python on Amazon