Zolcal - D 120ml
Liquid calcium is easier for the body to metabolise and absorb than powder so it can be used less often, more like 2-3 times a week with the food (not in the water as gliders do not generally drink much and the dosage cannot be guaranteed).
Zolcal D is a universal liquid formulation of Calcium and Vitamin D3, so not only can it be used as standard with gliders, its good for rescues or to help aid hind leg paralysis (as well as going to a good vet). If you have reptiles it is also used quite regularly with them.
recommended dosage: 0.1ml per 100g of animal weight. It is important to weigh your gliders on a regular basis, so using this should be quite straight forward, but yoghurt drops are always a good bribe to keep a glider still long enough to get a weight.