It lies near the village of Llanbedrgoch and is a North Wales Wildlife Trust reserve, a Site of Special Scienific Interest (SSSI) and a National Nature Reserve (NNR). It is also included in the Anglesey Fens Special Area of Conservation (SAC). Cors Goch is a valley mire and a lime-rich fenland. It has a layer of peat that exceeds 3m deep in places. It has a somewhat wetter western compartment where Llyn Cadarn is situated. It supports many rare wetland plants, and has extensive reedbeds, as well as areas of acidic heathland. It has a wonderful collection of wild orchids, including green veined orchid, northern marsh orchid, fragrant orchid, and the nationally scarce narrow leaved marsh orchid. Additional rare plants include marsh dandelion, the nationally scarce fen pondweed, and dwarf stonewort in areas of open water. Marsh birds and waterfowl frequent the reserve, including reedbed specialists such as grasshopper warblers, sedge warbler and reed bunting. The area hosts a wealth of insect life including the small copper, small heath and small pearl-bordered fritillary butterflies. In addition to this, over 250 species of moth have been recorded, and there are also many different kinds of dragonflies and damselflies. The site’s complement of amphibians and reptiles includes great crested newts and adders. The reserve is best accessed from the eastern end of the site, where it is possible to park on the roadside.

There is also a footpath along the southern boundary of the fen, and a (partly submerged) boardwalk which enables access to the dense fen areas.