Whisk fern  (psilotum nudum)

Anyone here grows the Whisk Fern (Psilotaceae: Psilotum nudum)?

My plant is not doing well and I am wondering if the potting mix that I use is not correct. I am currently using a sandy, loamy mix for growing cacti. I live at the equator (hot, humid Singapore&#33 .

Woops. Wrong forum. Could a moderator please transfer to the Bromeliads, Tilandsia, Ferns forum? Thank you very much!