Cubaris sp. 'Black Diamond' Isopods

Most Cubaris trade in warm browns, oranges and pastels. This one goes the other way: cool, dark, grey-purple, with a pale tail. And, unusually, it wants to be kept cooler too. Cubaris sp. 'Black Diamond', sometimes listed as 'Diamond Black', 'Quartz' or occasionally 'Diamond Tiger', is one of the more distinctive premium species in the UK hobby, and still a fairly rare one. If you have spent time with the warm-toned morphs and fancy something with a different character, this is the isopod that delivers it.

The body runs a deep grey through to a purplish cast, set against contrasting rear segments that fade to near-white or pale yellow at the tail. It is a mineral, gemstone sort of look, and it reads as cool where the rest of the genus reads as warm. Under brighter light the purple in the body lifts and the pale tail segments stand out sharply; in ordinary room light the overall read is a dark, slaty grey with a bright rear. Size helps too: at around 14mm, 'Black Diamond' sits at the larger end for Cubaris, so this is a substantial display animal rather than a speck you squint at. Disturb one and it rolls into a tight, armoured ball, classic Cubaris behaviour, before unfurling once things settle.

In a collection it works as the dark, cool counterpoint to the warmer premium morphs. Set it alongside Rubber Ducky, Red Edge and Lemon Blue and the contrast does a lot of work on a shelf. It sits within our wider Cubaris collection, and it is worth drawing one clear distinction: do not confuse the cool-kept Diamond with the solid-black Black Sapphire, which is a warm-care species. The two look superficially similar in a listing photo but want opposite ends of the temperature range.

That temperature preference is the thing to get right. Unlike most warm-tropical Cubaris, 'Black Diamond' does best at ordinary UK room temperature and dislikes heat, so keep it on the cooler side, roughly 18 to 23°C, and away from radiators, heat mats and sunny windowsills. It still wants humidity in the 65 to 80% band with a clear gradient across the tub, plus gentle ventilation to keep the air moving without drying everything out. Give it a deep, living substrate built from flake soil, rotted hardwood and organic topsoil, and skip a plain coco-coir base, which does little for this species. Keep calcium permanently available as cuttlebone or crushed limestone, and lay leaf litter and cork bark across the surface for cover and grazing. Feeding is simple: white rotten wood and leaf litter do most of the work, topped up with the occasional slice of veg and a little protein.

Breeding is slow and steady rather than explosive, very much in the premium Cubaris mould, so this is one for patient keepers who enjoy watching a colony build over the long haul. Give it stable cooler conditions, plenty of calcium and as little disturbance as you can manage, and it will tick along quietly and reward the wait. If you are newer to the genus and want something more forgiving to learn on first, start with Cubaris murina and come back to the Diamond once your technique is settled.

Every colony leaves us captive-bred, packed around a ventilated tub of damp sphagnum inside a double-walled box, and sent out Monday to Thursday on tracked next-day Royal Mail for delivery by 1pm. Each order carries our live-arrival guarantee and a 20% overcount as standard, so you begin with a little more than you paid for.