Its Nerite snails that do that Dave, and yeah, its just a nightmare haha theyre welded into the bogwood, quite literally. Unfortunately, Nerite eggs need to be laid in brackish water to hatch out.
The apple snails lay their eggs in large batches all bonded together out of the water, whats more, the apple snails eggs will most likely hatch.
Snails really are amazing creatures, not only doing a sterling algae job but providing a very nice focus.
My substrate is plain aquatic compost under sand with some black slate gravel mixed in from years ago. its nice as the current exposes the slate in places in fuller flow. The shrimps also feed off some of the algae on the gravel in those places, so its almost like a lure to get the illusive buggers out.