My husband says this is a type of harmless "sponge"...I am not so sure. Our 20 gal tank is about 8 months old, we know we have some aptasia (trying to deal with it...sigh). These soft, small branch like things seem to be multiplying rapidly on the rocks. Any advice gladly taken as to 1) what they are and, if a pest, 2) the best way to deal with them! Sorry I am not the best videographer :-0