It is difficult to maintain a marine planted.. Been there and done that... Not many true vaacular marine plants we can get in Singapore...
I only found Zostera sp, a few Halophila sp and some Thalassia sp... Have not kept them long term so not sure how hardy are they...
Caulerpa is a no no as they will go asexual after sometime with exception of C. prolifera...
Also have tried Gracilaria sp... Will melt after sometimes...
Udotea sp will turn white if not enough calcium and Kh in your tank...
Ulva sp is quite okay but you need to find a way to stick them to a rock if not it will float around...
Marine Planted will require dosing of Iron for the plant, they absorb Iron...