Guardian of the Corals, the red-spotted coral crab, is one of the rarest ornamental crabs you can find in stores. It has gained quite a bit of fame for its appearance and mutualistic relationship with corals in recent years. They are relatively easy to find in stores, but despite their availability, there is not much organized information about keeping them.
With a few crucial exceptions, they are comparatively easy to care for. Here, you’ll learn everything you need to know about red spotted coral crabs to keep them thriving.
Quick overview of red spotted coral crab
| Names | Rust-Spotted Guard Crab, Red Spotted Coral Crab, Polkadot Guard Crab, Acropora Crab, Trapezia Pocillopora, Red Spotted Trapeze Crab |
| Scientific name | Trapezia rufopunctata |
| Synonyms | Cancer rufopunctataGrapsillus maculatusQuadrella rufopunctataTrapezia acutifrons |
| Care level | Medium |
| Habitat type | Marine |
| Reef compatible | Yes |
| Size | 5 cm – 6 cm (1.97 to 2.36 inches) |
| Color | Pinkish white, Maroon, Red and Orange |
| Diet | Carnivore |
| Sleeping nature | Nocturnal |
| Depth | 0–30 m |
| Optimal Temperature | 22 °C to 30 °C (72 – 82° F) |
| Temperament | Peaceful |
| Mating | Indirect sperm transfer and courtship ritual |
| Lifespan | Up to 5 years |
Habitat and Distribution
It lives on Pocillopora corals in shallow water at a depth of 0–30 meters and can be found widespread through the Indo-Pacific region and the Great Barrier Reef in Australia and Bali, Indonesia.
Classification
- Kingdom:Animalia
- Phylum: Arthropoda
- Subphylum: Crustacea
- Class: Malacostraca
- Order: Decapoda
- Infraorder:Brachyura
- Family: Trapeziidae
- Genus: Trapezia
- Species:T. rufopunctata
Red spotted coral crab facts
- Symbiotic relation – The red spotted crabs have a mutualistic relationship with the hard corals such as Pocillopora, Stylophora, and Acropora. They spend most of their lives in the corals.
The corals get protection from crown-of-thorns starfish provided by the red spotted coral crab. In exchange, the crabs receive food in the form of mucus and coral tissue, as well as fallen debris and protection from the branching calcareous skeleton.
Their primary food source, mucus, is obtained from massaging the polyps of the corals with their legs until the polyps release slimy mucus, which they eat by collecting with the hairs on the lower part of the legs. They clean the corals by removing debris and increasing water flow, which helps prevent coral tissue death.
- Appearance – Their body is covered with a mottled pattern; from 100 to 200 red spots over a pinkish white background, and from there they got their name. The unique appearance is believed to help them camouflage with the colorful coral habitat.
An attractive part of their appearance is their green, ghost colored eyes, which are a work of absolute beauty.
- Unique battle – The species avoids face-to-face confrontation; instead, they retreat to the coral, holding their large claws up defensively. Also, it is a shy crab that will hide most of the time in the branches of corals in your aquarium.
- True crabs – Many crabs, like the porcelain crabs and the hermit crabs, are considered to look like crabs but not true crabs; however, red spotted coral crabs are true crabs.
- Behavior – Typically, a pair containing a male and a female can be observed occupying a single coral colony, while larger corals are able to host 5 mating pairs.
Care for red spotted coral crabs
Tank setup
Size
If your setup is for only one or two crabs with a little coral colony, choose at least a five gallon tank. Go for a 20- to 30-gallon tank, if the tank will be lively and full of fish and crustaceans.
Substrate
Take a sand substrate, especially one made for marine aquariums. Choose the substrate according to other animals’ preferences, as the red spotted coral crabs don’t have much contact with the substrate.
Decoration
Bring some corals or at least a healthy one of the crabs’ preference; among the Pocilopora, Stylophora, and Acropora. The more you bring them, the more the crabs will get their habitat vibe.
Can’t they live without these corals? Well, yes, they can. However, they won’t be comfortable without them and won’t thrive for long as they won’t get their necessary food source, mucus or environment. They developed this behavior for thousands of years, and suddenly it can’t be changed in the aquarium.
Some aquarists believe that if the crab gets enough food (a substitute for mucus, the main reason for their living on corals), it can survive without having any problems.
My suggestion is to bring Pocillopora corals as soon as possible. You can go for anemones, other hard corals, soft corals or rocks while they don’t have access to the preferable corals.
Finish the setup with your preferred rocks or caves.
Water and temperature requirements
The temperature should be kept between 22 °C and 30 °C, which is a normal temperature for an aquarium. However, they are pretty adaptable to the temperature, as in some places, the red spotted coral crabs are found at 20 °C and even at 36 °C.
The dKH should be between 8 and 12, with a pH level of 8.1–8.4.
Feeding
Red spotted coral crabs are carnivorous, so forget about the vegetables or fruits, and it is even observed that they don’t like fish food.
Give them frozen food, chopped seafood, bloodworms, and brine shrimp. Keep a calcium source as an additive; provide a calcium source such as cuttlebone.
Tank mates for red spotted coral crabs
They are peaceful and will be busy doing their own stuff, let alone harming someone. The best would be to keep a male and a female, or a group of them.
You can consider keeping them with other trapezia, like the Trapezia Cymodoce. There is no worry about fish like the clownfish and dwarf tank cleaner hermit crabs.
