[Stones]

I've kept mangrove pods both in a HOB style refugium and in a sump refugium. I never had much luck with them after I started using chaeto algae for nutrient export as the chaeto will remove any excess nitrates or phosphates much faster than the roots of the mangroves can uptake them. I believe you can either have the roots free floating in the water by suspending the mangrove pod in a styrofoam float or you can anchor the roots into a sand substrate.

They do make very effective nutrient export devices if used in large enough numbers and kept in the proper conditions. 1 mangrove likely won't help much with nutrient export but they sure are nice to look at once they fill out with some leaves.

Also, be sure to mist the leaves of the plant off with fresh water a few times per week or it will die. As a result of uptaking fresh water out of salt water, mangroves will precipitate a salt residue on their leaves that needs to be manually removed.