From Microcosm Aquarium Explorer
The rewards of octopus husbandry can be had without selecting one that can kill you. The blue-ringed octopus has bitten and killed many people, mostly fisherfolk in tropical countries, and deserves utmost respect. Death is caused by tetrodotoxin, which is also found in pufferfishes, some triggerfishes, certain newts, and other animals.
The symptoms of tetrodotoxin poisoning include sweating, dizziness, termors, seizures, inability to breathe, nausea, vomiting, and irregular heartbeat or heart failure.
This smallish species is characterized by having a light tan to white body covered with rings or “eyespots” of a bright or iridescent blue that flash when the animal is under stress.
It can turn aggressive and is prone to bite, injecting maculotoxin into its victim; this can lead to rapid paralysis and may even be fatal as there is no antivenin.
Other common name(s):
Maximum length: 24 cm (9 in)
Maximum height: 28 cm (11 in)
Lighting: Diurnal cycle necessary. Dim to moderate lighting.
Water: Marine 24 °C (75 °F) - 28 °C (82 °F)
Prefers live foods (small fishes or shrimps).
POTENTIALLY DEADLY. VENOMOUS. NO ANTIVENIN CURRENTLY AVAILABLE. Should not be kept by any amateur aquarist.
Keeping a small octopus is probably the best way to have an interactive marine pet, but keeping a small blue-ringed octopus is simply inviting a tragedy to happen.