I've had this tank in operation 15 + years and over the last 5 years once and awhile i get outbreaks of these weird green tubular like growths. They spread quite fast and only solution seems to be manual removal and they just disappear. When you grab them and pinch with your fingers they seem to be soft but also calcified at the same time. Any idea what they are and any suggestions other than manual removal (which is a real PIA since they are in some many cracks and crevices.)