I use one of those sea sponges that people use to clean thier face. If you get unsightly buildup of of alge on plastic plants or rocks, you can take your dishwasher, run a empty load of nothing but white vinager through it, and then put your plants/rocks on the TOP RACK and just let it go with the hot water. You can use a bit of white vinager with that too if its REALY bad. Wrap your fake plants with cheeze cloth when they go into the washer. It will help them from getting too exposed to the heat and jets of water.