I use fine plastic fishing line that I searched for on Amazon or Ebay etc... useful stuff!!
I haven't got round to doing anything aquatic (might be a sneaky way into making my parents allow me a fish tank in the house!!) But going from a previous competition of growing plants in a bottle, I bought a big cookie jar and lid on Amazon and added gravel for drainage, carbon (helps reduce nasties) and potting soil and went and picked 3 species of moss from my local woods and a few weeds from the garden and planted it up (including moss tied to a branch) and then watered it using a little food for my orchids... take the lid off once a week for a few hours but other than that, self sustaining!! Looks very cool