There were many Nitidulidae beetles inside the compost bin, on top of the soil. Most of them seemed to have at least one red mite attached to them. Some beetles, like this one, carried a heavy load of mites. The mites were identified by a mite expert, via Ken Walker, as being a species of Mesostigmata.
Eight red legs, a metallic blue body and red mouthparts. It was rescued from a water bucket, ran around constantly and even tried to burrow into the hand that was holding it. It is an arachnid of some kind, but not sure if it is a harvestman, or a mite or a tick or a very unusual spider.