No, superglue is good to use for sticking stuff like frags and small pieces. It has no tensile strengh though, so it's easier to use milliput and so on for jobs like propping up pieces of rock.
Milliput is a 2 part non toxic modelling clay. The original is a creamy white colour, deltec and aquamedic (I think) resell it with a purple dye, but coralline covers it pretty quickly anyway. It is nontoxic, and will dry underwater (but dries faster, better out). It isn't especially sticky in my experience tho' |