HomeAquarium FishBlack Widow Anemone - Care, Characteristics & More

Black Widow Anemone – Care, Characteristics & More

Black Widow Anemone is a member of the invertebrate group Anthozoa, found in saltwater.

These creatures are named after the flowers of the windflower family (the name comes from the Greek word ‘those which means flower’) and their tendency to sway with even the slightest sea breeze.

Most species live in hard or stony coral reefs, while others can be found on rocksdebrismudsand, and basically, anywhere they can attach themselves.

Anemones are infamous for their symbiotic relationships, consisting of clownfish living within them while both benefit mutually. 

Black Widow Anemone, however, isn’t that type of anemone but instead another type that’s worth talking about due to its uniqueness! 

Black Widows are also known as Black Octopus or Black Maroon Anemones, but the common name Black Widow takes most of its fame. 

They are considered one of the most venomous anemones globally due to their various toxins, making them quite dangerous for aquarium keepers. 

Although Black Widows usually don’t attack humans, these animals must still be kept with great care and knowledge on how they interact with each other.


Black Widow Anemones can come in several colors, including bluegreen, or purple, while some rare ones might even have white “leaves” attached to them! 

Black Widows can grow up to 15 inches wide, while their tentacles tend to be short and stubby. They are usually found in deeper waters, but they can also be spotted in shallower areas since their habitat ranges from the water’s surface to 50 meters deep.

Black Widow Anemones have both male and female sexes, making them perfect for breeding purposes.


Anemones will reproduce in the wild black widow by splitting themselves in half, creating two black widows. 

In aquariums, black widow anemones can reproduce asexually by creating clones to start new black widow anemone colonies. 

This is done through a pedal laceration process in which a black widow anemone’s foot attaches to a rock or piece of coral and then starts replicating into its black webbed pieces that will eventually break away from the base and float around nearby, looking for space to set down roots.

Black Widow Anemones are only known to have one symbiotic relationship with their prey, Symbiodinium algae, but they could have up to eight symbiotic relationships with other organisms. 

Characteristics of Black Widow Anemone


As you might’ve guessed, Black Widows are highly venomous animals which means that humans must always wear protective gear while handling them or performing maintenance on their aquariums. 

This venom is produced by nematocysts within the Black Widow’s tentacles, injecting it into any attacker upon contact, thus causing extreme painnumbnessswellingparalysis, or even death if not treated correctly.

Black Widow venom is extremely powerful. Even with no symptoms, an individual will usually die due to a lack of oxygen (the Black Widow’s toxin prevents blood from carrying it throughout the body, making its victim unable to breathe).

This doesn’t mean that Black Widows are sold for their venom, though. Black Widows are collected by divers who then sell them for up to $1,000’s. 

Black Widow anemones are quite popular due to their unique look, plus they can be both easy or hard to maintain depending on how well they’re taken care of. 

Black Widows don’t have any specific requirements, but you do need a lot of knowledge about their behaviors before you can safely own one!

These should always be kept alone since they can become quite aggressive if kept with other Black Widows or even any kind of anemones. 

They need to be placed in a tank at least 3 feet long and no less than 60 gallons since Black Widows are very active animals which means they produce a lot of oxygen (they’re constantly “blowing” water out). 

Their substrate should consist of crushed coral, while their lighting system must provide them with 8 hours of darkness.

These anemones can grow very quickly, so it’s recommended to check up on your Black Widow regularly and regularly re-arrange the rocks inside its tank (this way, it won’t suffocate and will continue to eat and breathe normally)

It’s also important not to accidentally drop tiny Black Widows (their offspring) down your drain since Black Widow anemones can reproduce asexually! 

Black Widows should be fed clamsshrimpmussels, and even fish every day. 

Black Widow venom can’t kill you, but it does cause pain and paralysis, which means that Black Widows must always be kept away from children or anyone who might accidentally touch them.

Black Widow anemones are usually recommended for intermediate to expert aquarists since they require specific water chemistry to survive and a lot of attention, so they don’t die due to lack of food or suffocate if their rocks aren’t arranged properly. 

Black Widows aren’t the easiest animals to maintain, so please only purchase one if you have the necessary knowledge experience and are truly willing to commit yourself to Black Widow care. 

These anemones are truly unique animals that will surely add some diversity to your aquarium setup; plus, they look very cool so they can be a wonderful addition for any aquarist. 

They might not always have the best temperaments, but if cared for properly, this shouldn’t matter since Black Widows become perfect pet companions with time. 

Black Widow anemones are great pets but please only purchase one (plus all other marine creatures) if you know what you’re doing since they aren’t easy animals to maintain, and it’s not recommended for beginners.

Black Widow Anemone Care


The black widow anemone is native to the South Pacific Ocean. They are black with white spots and eight tentacles coming out of the top. Their venom is extremely strong, so handling them should be avoided at all costs.

Black Widow Anemones can survive in aquariums that meet specific parameters: low salinity (specific gravity 1.020-1.027), less than 8 degrees dH, and a pH between 8.1 and 8.4. The ideal water temperature is 72°F (22°C).

There are black widow anemones in the wild ranging from 1 inch – to 2 feet (0.3-0.6 meters). 

In aquariums, they should be kept at least 5 inches (12 centimeters) deep to make sure they get enough oxygen exchange for their symbiotic algae to survive. 

The black web pattern on them helps keep symbiotic algae living inside of them, but there must also be adequate lighting, or else the algae will die and lead to the death of the black widow anemone as well.

They need calcium supplementation added into the water to keep their exoskeleton from deteriorating. 

This can be done by putting a cuttlebone in the tank or calcium ionized into the water through a calcium reactor. They also need iodine to promote proper growth and health.

 It is not advised that black widow anemones be handled directly because they have extremely strong venom that can cause intense pain and possible paralysis for days at a time unless treated by a physician.

To properly take care of black widow anemones, black background with bright white spots to mimic its natural habitat should be used because black acts as camouflage against predators or other threats. 

In contrast, its white spots allow it to blend in with surrounding corals from above but still look black from below, so enemies cannot detect it. To keep black widow anemones healthy, they need to be accompanied by other corals that do not sting them. They are best kept away from other types of stinging creatures, including but not limited to:

  • Anthozoans (corallimorpharians, zoanthids, palythoa).
  • Sea stars or other echinoderms.
  • Nudibranchs.
  • Other black widows.

Black Widow Anemones eat brine shrimp and should be fed once a day if possible. If you can’t feed them at least twice a week, then pre-packaged frozen plankton will suffice. Black widow anemones sit in wait for food at night with their tentacles outstretched towards prey that comes near enough to grab.


Black widows are a beautiful and interesting species of anemone that can inhabit the waters near reefs or shallow lagoons. 

They have a black base with bright red tentacles, which they use to capture prey items for food.

It is important when aquarium shopping to ensure that you purchase a tank large enough so your new pet has plenty of room to grow, but not too big where it will become overcrowded quickly. 

It would be best to consider whether other invertebrates live in this size range because they may fight over the territory once introduced together. 

They require care, but it isn’t hard to take care of them in your home aquarium. You will have no problem taking on this responsibility with the tips mentioned above.

Fishkeeping Expert
Fishkeeping Expert
With years of collective fishkeeping knowledge, we are pleased to share the tank maintenance tips and fish care advice we've picked up along the way. Fishkeeping Expert is home to all fishkeeping tutorials and guides that will help you keep your fish healthy.


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