Out in the wild with all the littering people do espically in the ocean, the bottles will serve as homes for certain species. Im still debating if i want to keep them in there. The idea is to break the bottle towards the bottom that way certain fish can get in/out with ease. I left the lids off cuz they rust and I wouldnt want that. Not all glass is reef safe though. It cant be painted glass but you can keep the label on it as long as you seal it. Eventually if I keep the bottles there will be zoas growing on them along with coraline, etc... Also if I have a mated pair of fish and they decide to reproduce (hopefully) it will happen in the bottles (keeps eggs safe from bigger fish).