I want to make a nice sandy and rocky looking setup for the 20 gallon we just got! So today I went out to our local beach and gathered about 10 nice rocks and a nice amount of shells. And slo went to our local craft store and bought 200 sea shells for $2.00. Now here's my question if I scrub the rocks and shells really well and then boil them both, will they be safe to use? I want to make this tank for a 2 pairs of shell dwelling cichlids? Opinions please and has anyone ever used rocks and shells you've found successfully?