for two of the plants i made a weight out of plaster but the plaster went soft and flakey in the water......
i then made the weight out of acrylic in work but it wasnt heavy enough to stay put.
im going to look at wood and volcanic rock to tie the plants too.
I did think of glue but wasnt sure if it was safe or not.
i have a bit of pennywort but i need more and then i need to get it tied to something so the filter doesnt pull it towards it