LARGER SYSTEM SPECIES. 250-LITRES AND OVER
OCTOPUS
6Scientific name: Octopus bimaculatus and Octopus vulgaris 6Distribution: Tropical Indo-Pacific, Octopus
vulgaris is found in tropical and temperate seas worldwide. 6Price Range: £45-250
6System Size: Octopus demand excellent and stable water quality. Richly oxygenated, low pollutant water is difficult though not impossible to achieve in small aquaria, but easier to provide in larger volumes. It can be good to provide octopus with extra space so that they can explore and forage as they would in their natural environment hence inclusion in the section for larger species — 250 litres minimum but ideally more.
With the popularity of the BBC’s Octopus in My House and Netflix’s My Octopus Teacher it is necessary to highlight what, for many, is the ultimate inhabitant of the single-species aquarium: the octopus.
These molluscs tick practically every box for the aquarist; fascinating, unique, intelligent, and interactive — but their husbandry demands a system entirely dedicated to their needs. They also require filtration capable of dealing with large amounts of waste, as an octopus has a large appetite yet needs high levels of oxygen in its impeccably clean water.
Lighting need not be too intense; a degree of controllability or dimming is useful as some individuals become more active at night, and the aquarium must be escape proof — no rimless modern-looking open topped aquarium for an octopus. No gap is too small for these animals to flee their residence, and they’re able to squeeze through any hole large enough to fit their tiny, rigid beaks.
For many, the greatest challenge of keeping any species of octopus is the short lifespan. Most species of appropriate size for the home aquarium live for less than two years and will be adolescents by the time they are acquired. Some, such as the smaller species of Mimic octopus, Thaumoctopus mimicus, and Wonderpus, Wonderpus photogenicus, (both available in the UK hobby despite being uncommon in their natural environment) may be fully grown when acquired and their lifespan even more limited.
Given the level of interaction they can offer and just how tame they become, their inevitable deaths can be upsetting for those who experience it.
UNDULATE TRIGGERFISH
6Scientific name: Balistapus undulatus
6Distribution: Tropical Indo-Pacific
6Price range: £25-55
6System size: Reaching around 30cm, this triggerfish demands a large aquarium. In the long term a 700-litre, well-filtered system would be an absolute minimum but size can be increased as it grows as juvenile individuals are available from around 3cm upwards.
A fish reputed for being one of the most downright nasty species widely available in the hobby, the Undulate triggerfish is often the victim of poorly-researched stocking attempts that result in it wiping out all of its tankmates.
Like many such fish it’s available at temptingly small sizes, and initially it can be shy and reclusive, giving the aquarist a false impression of its suitability for an established aquarium. From an interaction perspective it’s an absolute star; it’s highly intelligent and it will become notably tame as it matures. Aquarists can expect it to engage with them and should provide areas to explore and environmental enrichment to keep it stimulated — offering food in shells that require crunching with their powerful jaws and strong teeth, for example.
Fish such as this — and there are many with similar characteristics — are absolutely ideal for the species-only aquarium; they are large and beautiful enough to hold their own as a display with the added bonus of fantastic behaviour and interactions with the aquarist. Why bother risking them with other species when they have so much to offer in their own right?