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Vocab & Jargon A-C

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40 Gallon Breeder Tank

A 40-gallon tank with the dimensions 36″ x 18″ x 16″.  There are many tank options out there that are 40-gallons, but only the 40-gallon breeder has these exact dimensions.  It is longer and shorter than a traditional aquarium, so it provides more horizontal space for breeding fish.  I use a 40-gallon breeder for my quarantine tank.

If at all possible, don’t buy this online!  Wait for Petco or Petsmart to have one of their aquarium sales, and you can buy this for around $50-$60, not $250!!

black rimmed 40 gallon glass aquarium on white background

Actinic Light

Actinic bulbs typically emit blue light which is considered beneficial for coral growth. These bulbs fit into flourescent fixtures

close up of actinic light bulb connectors

Activated Carbon

A form of chemical filtration, activated carbon is highly absorptive heated charcoal that helps remove heavy metals, odors, and compounds that can color your water. Overuse can also lead to the removal of certain trace elements necessary for coral growth.  I only use ROX 0.8 on my tanks!

Clear plastic bottle with activated carbon inside

AIO Tank

Stands for “All In One”, but is a bit of a misnomer. Most AIO systems come with a tank and filtration media, but that is about it. Most AIO tanks require additional equipment such as lights, pumps, and heaters. Below is the an example of an AIO tank from Waterbox Aquariums.

10 gallon glass aquarium full of colorful corals and saltwater fish

Air Pump

Used during power outages, when treating your tank with certain medications, or when additional oxygenation is necessary, an air pump is usually attached to an air stone to provide temporary or increased aeration to your system.

battery powered air pump with blue air stone on white background

Air Stone

Usually attached to an air pump, an air stone is a porous piece of ceramic that creates a large amount of bubbles in your aquarium to increase aeration and oxygenation.

8 blue airstones on white background

Airline tubing is any sort of flexible tubing, which in the saltwater aquarium hobby is usually clear plastic that comes in 3/16th of an inch. Especially useful with air pumps and drip acclimation.  Called airline tubing because it is usually used for air, and not for water.  In the aquarium we often use airline tubing to help drip acclimate our livestock.

blue silicone airline tubing rolled up in packaging

Algae Scraper

A handheld device used for scraping algae off of your glass or acrylic tank. Usually comes with various attachments: stainless steel for glass, plastic for acrylic tanks, or just a sponge like material for easy to remove algae.

adjustable length algae scraper with accessories in original packaging

Algae Scrubber

A form of chemical filtration, an algae scraper is any sort of device that uses light & water to grow algae. Typically a scrubber is some sort of self contained box that sits above the water line. Water from your tank is pumped through it and over some sort of mesh screen. Light is added to grow algae.

The thinking behind an algae scrubber is that by growing algae, you can help not only remove phosphates from your water, but you can also outcompete nuisance algae that may grow in your display tank.

closed algae reactor on white background


Simply put, alkalinity is the “ability of water to resist changes in pH” (Wikipedia). Maintaining an alkalinity between 7-12 dKH is important to your aquarium for several reasons: It prevents pH swings and is crucial for your corals to form calcium carbonate skeletons.  Alkalinity is added to your aquarium by means of water changes or through 2-part dosing.

two 1 liter white jugs side by side on white background


Ammonia in your aquarium is the result of decomposing organic matter such as fish food or waste. Even small levels of ammonia can be toxic to your fish. Ammonia is a natural part of the nitrogen cycle, and once an adequate biological filter has been established, a saltwater aquarium can usually convert ammonia into nitrite and nitrate.


Shrimp like in form, amphipods are small crustaceans often used as a live-food source for various saltwater fish, expecially Mandarin Dragonettes. Usually signifianctly larger than copepods

microscopic closeup of amphipod on black background
By Michal Maňas - Own work, CC BY 2.5,

Anaerobic Bacteria

This bacteria can be found in the saltwater aquarium either deep inside live rock or near the bottom of a deep sandbed.  It is a special kind of bacteria that does not use oxygen. Rather, it takes the oxygen molecule directly from nitrate, turning it into nitrogen gas. So anaerobic bacteria is super helpful in reducing nitrate in your tank, as nitrogen gas can just bubble out of your system.


Also known as a Sea Anemone, anemones are marine predatory animals with stinging tentacles to help capture food. A primary difference between coral and anemones, is anemones are mobile and can move around, whereas corals are sessile, meaning fixed to one place. Hobbyists often refer to anemones as nems, condys, bta’s, or rbtas.

Rose Bubble Tip Anemone top down view
© My First Fish Tank, 2019

Just like we landscape a yard, we aquascape an aquarium. An aquascape is usually comprised of various pieces of live rock put together in such a way as to provide adequate housing for fish and corals

70 gallon aquarium with purple rocks and no water
© My First Fish Tank, 2019


Aragonite is a common form of calcium carbonate that makes up hard coral skeletons and invert shells.

In the saltwater aquarium hobby you generally find aragonite as either part of a substrate (sand or rubble), or in a calcium reactor.

When used as large rubble in a calcium reactor, it is broken down and provides calcium and alkalinity to your inverts.

close up product picture of aragonite fragments in clear packaging


Automatic Top Off. Auto top off water is the RO/DI or distilled water used to replace daily evaporation in saltwater aquariums. Auto top off can also refer to an automated pump/sensor that will refill the tank for you.

close up view of auto top off unit on white background

Auto Top Off

Automatic Top Off. Auto top off water is the RO/DI or distilled water used to replace daily evaporation in saltwater aquariums. Auto top off can also refer to an automated pump/sensor that will refill the tank for you.

auto top off accessories laid out flat on white background

Bare Bottom Tank

A saltwater aquarium that does not utilize any sort of substrate.

40 gallon saltwater aquarium with purple rock and fish
© My First Fish Tank, 2019

Bean Animal

An overflow style that combines both the Durso Standpipe and the Herbie Overflow method. Requires three holes, one being for the adjustable Herbie drain, the second for the Durso Standpipe, and the third for the emergency drain. A silent overflow system capable of large amounts of water.

infographic of bean animal style filtration system

Beneficial Bacteria

There are many, many types of beneficial bacteria, and hobbyists can be referring to a lot of different things.  But usually, in the saltwater hobby, beneficial bacteria refers to nitrifying bacteria that helps convert toxic ammonia into a less toxic nitrate.

Basically, beneficial bacteria are what colonize on your live rock, sand substrate, sponge media, and ceramic media, to cycle your tank.  

Beneficial bacteria will occur naturally by themselves, as long as there is ammonia present.  How do you make ammonia present you might ask?  Well, you can either add ammonia to your tank, or do what most of us do, add some sort of biological matter to your tank and let it decompose. This could be fish food or even a piece of frozen shrimp.

To learn more about how to cycle your tank, click HERE

Close up product picture Dr. Tim one and only

Berlin Method

This is a method of filtration that relies on live rock and a protein skimmer. Basically most modern saltwater aquariums with sumps use this method to some degree.

Bio Balls

Usually made of plastic or ceramic media, bio balls provide a large surface area for beneficial bacteria to colonize thus providing biological filtration. More common in the freshwater hobby as they are placed in canister filters.


The bioload, or biological load, is the toal amount of livestock waste in your tank. If your bioload is too high, that usually means that you have an insufficient amount of biological filtration. Your maximum bioload is equivalent to the maximum amount of livestock you can have that your live rock, live sand, and other biological filtration media can safely handle, meaning turning all of the ammonia into nitrite and nitrate. If you start detecting ammonia in your tank, your bioload is likely too high.

Biological Filtration

This is the biological process whereby beneficial bacteria break down ammonia (which is toxic to your livestock) into nitrite and nitrate. In most saltwater aquariums, beneficial bacteria colonize on/in the live rock, live sand, and ceramic media plates/balls, and sponge filters.


These are small pellets made of a biodegradable polymer that beneficial bacteria love. The biopellets are slowly consumed by the beneficial bacteria. Biopellets are helpful in removing nitrate from the water column.

white biopellets in clear plastic jug

Broadcast Feeding

A method of feeding corals and other filter-feeding invertebrates that involves pouring the food into your tank and allowing the wavemaker to deliver it to your animals.  The opposite of this would be target feeding.


Bubble Tip Anemone. RBTA– Rose Bubble Tip Anemone.

Rose Bubble Tip Anemone top down view
© My First Fish Tank, 2019


Bulkheads are used in the aquarium hobby to create a water tight seal between the “wet” side of the aquarium and the “dry” side of the sump or overflow. Most commonly, bulkheads are used in the rear or bottom of a tank to attach pvc or flexible tubing to your sump.

1" black pvc bulkhead on white background


An important element in saltwater aquariums because it is one of the building blocks for corals. Stony corals use calcium to form their calcium carbonate skeletons. Also important for the shells of invertebrates.

manufacturer plastic bottle with powdered calcium inside

Calciumn Carbonate

Do you want the scientific definition or the easy definition?  Let’s do both.  First the scientific:

“Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks as the minerals calcite and aragonite (most notably as limestone, which is a type of sedimentary rock consisting mainly of calcite) and is the main component of pearls and the shells of marine organisms, snails, and eggs.” Wikipedia

Basically, calcium carbonate is Tums, those little things you chew when you have indigestion.  It is an essential building block for the hard part of stony corals, as well as the shells of snails and the exoskeletons of crabs.  In an aquarium, we have to replace calcium carbonate that is being used by our inverts by either performing water changes, or dosing it back into the tank manually.

But invertebrates typically use calcium carbonate and alkalinity in equal measure, so you typically have to dose both, hence the term, 2-part dosing!

two 1 liter white jugs side by side on white background

Calcium Reactor

Calcium reactors are used in the saltwater hobby as a means of efficiently adding calcium and alkalinity to the water column. A calcium reactor is comprised of the reaction chamber, a pump, media (aragonite), and CO2. The CO2 is fed into the reaction chamber, thus lowering the pH and making the water slightly acidic. The acidic water breaks down the aragonite, thus releasing calcium into the water column.

Canister Filter

Most common in the saltwater hobby, a canister filter is a separate container that contains a pump and various types of filtration media. Water is pumped through the canister, thus interacting with the various filtration stages before being returned to the display tank.

green freshwater canister filter on white background

Carbon Dosing

A method of increasing the food supply (carbon) for beneficial bacteria in your tank. Vinegar, vodka, or specialized products are often added to the water column to provide “food” for beneficial bacteria.

Ceramic Media

In essence, ceramic media has a similar purpose to live rock: it provides surface area for beneficial bacteria to colonize.

You can most commonly find ceramic bio-media either in round balls, bricks, or plates.

Ceramic media is especially useful in saltwater aquariums with a high bioload, usually do to a high amount of fish.

Sometimes, especially for those of us who like to overstock our tanks, our live rock and substrate do not provide enough surface area for beneficial bacteria to keep up with the demands of converting ammonia to nitrate.

Ceramic media is usually placed in the sump, and enhances biological filtration by providing more space for nitrifying bacteria to colonize.


Caulerpa is a kind of seaweed often used in saltwater refugiums. As the caulerpa grows, it consumes phosphates, thus removing them from the water column. Then, when you remove the caulerpa, you are removing phosphates from the water column. Caulerpa is a popular type of macro algae used in refugiums to help control unwanted algae growth in the display tank.

green caulerpa macroalgae in saltwater aquarium
Dr. Robert Ricker, NOAA/NOS/ORR [Public domain]


Chaetomorpha, or chaeto for short, is a type of macro algae often used in saltwater refugiums. As the chaeto grows, it consumes phosphates, thus removing them from the water column. Then, when you remove the chaeto, you are removing phosphates from the water column. Chaeto is a popular type of macro algae used in refugiums to help control unwanted algae growth in the display tank. All macro algae can also provide a safe place for the breeding of amphipods and copepods.

ball of green chaetomorpha macroalgae in clear bottle

Chemical Filtration

Chemical filtration in the aquarium hobby comes in many forms, but is basically the use of chemicals to remove certain unwanted things from the water. The most common type of chemical filtration is the use of activated carbon and GFO (Granular Ferric Oxide). Activated carbon helps remove heavy metals and odors from the water, while GFO removes phosphates.


A chiller is an air conditioner for your aquarium. You plumb the chiller so that warm water from your tank enters, passes over the cooling element, and returns to your tank.

1/2 horsepower brown saltwater aquarium chiller on white background


Chloramines are disinfectants commonly used to treat public drinking water. Chloramine is created by adding a small amount of ammonia to chlorine. Chloramine is often used because it is longer lasting and does not react with other contaminants in the water.  Chloramines need to be removed from tap water because they are not safe for fish.


Chlorine is a chemical element most commonly used as a disinfectant for public drinking water. It is not healthy for livestock.

Clean Up Crew

A collection of livestock, often snails and crabs, that help keep your tank clean by consuming unwanted algae, leftover food, and even fish waste.

6 trochus snail shells on black background
H. Zell [CC BY-SA 3.0 (]v
blue legged hermit crab halfway out of shell in saltwater aquarium
RevolverOcelot [CC BY-SA 3.0 (]

Closed Loop

When speaking of a closed loop system in saltwater aquariums, we are basically referring method of water circulation where a pump (either submersed or external) is plumbed at both the intake and output. Water is then sucked out of either the display or sump, and then returned to the display or sump. For example, in an open loop system that uses a sump and submersible pump, when the pump is turned off, the siphon will stop and the water level will change in the sump and overflow. But in a closed loop system, when the pump is turned off nothing will happen, because there is no air involved.


A colorimeter is a type of testing device that uses a sensor to interpret a certain wavelength of light.  Basically, it reads the color for you, giving you a more accurate reading that doing it yourself.  With basic test kits, you hold up the vial to a color chart and do your best to match the two, thus giving you a reading.  With colorimeters, the device does the reading for you, giving you a more accurate result.

Community Tank

A community tank is a saltwater aquarium full of non-aggressive fish that live together in a community. The opposite would be a predator tank designed around one specific livestock that attacks and consumes the other members.

120 gallon saltwater fish tank with corals and live fish
© My First Fish Tank, 2019


Short for Condylactis Gigantea Anemone.

green and orange sea anemone
By Nhobgood Nick Hobgood - Own work, CC BY-SA 3.0,


A piece of equipment used to help control certain parameters such as temperature, pH, ORP, etc. They range from a simple and inexpensive temperature controller which turns your heater on and off, up to an expensive controller with multiple controllable outlets and complicated programming software with various probes.


Small crustaceans that are often added to saltwater tanks to provide a food source for fish. Typically much smaller than amphipods.

10 different colorful species copepods on black background
By Andrei Savitsky - Own work, CC BY-SA 4.0,


Sold under several different brand names such as Cupramine, copper is used to treat various fish diseases in a quarantine or hospital tank. Copper is highly toxic to invertebrates.

white plastic bottle of seachem cupramine


Sessile (not mobile) marine animals (invertebrates) that typically live in colonies with many identical polyps. SPS– Small Polyp Stony.  LPS– Large Polyp Stone. Softy– Soft Coral.

plating coral colony in coral reef with blue water
By Toby Hudson - Own work, CC BY-SA 3.0,

Coral Dip

Coral dip is used to “clean” corals of unwanted “hitchikers” before adding to your quarantine or display tank. You would mix the coral dip solution with saltwater, and then immerse your coral for a specific time, using either a pump or baster to gently “blast” the coral to remove unwanted pests.

blue glass bottle of coral rx dip

Coral Glue

Commonly this is just a thick gel superglue used to attach corals to live rock.

superglue gel squeeze bottle

Coralline Algae

A red encrusting algae often seen as desirable in saltwater aquariums.

purple coralline algae on glass
By FalsePerc, CC BY 2.5,


Clean Up Crew. A collection of livestock, often snails and crabs, that help keep your tank clean by consuming unwanted algae, leftover food, and even fish waste.

6 trochus snail shells on black background
H. Zell [CC BY-SA 3.0 (]v
blue legged hermit crab halfway out of shell in saltwater aquarium
RevolverOcelot [CC BY-SA 3.0 (]


A copper treatment used to treat a variety of fish diseases such as Marine Velvet and Ich. Highly toxic to invertebrates, so usually only used in a quarantine or hospital tank.

white plastic bottle of seachem cupramine


Also called Cyano, a photosynthetic bacteria, also known as blue/green algae or red slime algae, is often considered undeseriable in an aquarium. While not dangerous to your livestock, it can completely cover your entire tank in no time and is unsightly. There are various madications you can use to get rid of it.

purple cyanobacteria on white sand bed


Short for the Nitrogen Cycle. In an aquarium, the nitrogen cycle refers to various stages involved with turning ammonia into nitrate. Hobbyists will often say “My tank is cycled”, which means that beneficial bacteria have colonized and decomposing waste is now successfully being transformed from toxic ammonia to nitrates. In a saltwater aquarium, this process usually takes several weeks.

nitrogen cycle infographic