i just took one from my freshwater tank to put in my seahorse tank and i used bleach. The algae was caked on there so bad that i didn't even know it was yellow! haha all this time i thought we had an ugly green fake plant in there but when i bleached it the algae came off and tah duhh its a yellow/orangy one. I used a mixture of bleach and water and rinsed it very very well afterwards. I also let it dry completely and then re rinsed it again before putting it in the tank