Me and my group is very much active in rehabilitating reefs here in the Philippines where in dynamite fishing and other distructive fishing methods is still being practiced.
One method that seems to be quite effective is deployment of reefballs.
We use cement to make this reefballs or cement tubes with holes to be an artificial habitat for fishes, does anybody here have any suggestions for an alternative cheaper material to be used as reefballs that will not harm the environment. Thanks