Here is a customer's HOG3 in high-nutrient saltwater, and positioned slightly above the waterline. The high nutrients cause the very dark green slime growth, which is loaded with nutrients from the water (darker = more nutrients), and the air bubbles and salt spray are kept inside the case so that only air goes out the top hole. This dark growth will need brushing out with a toothbrush in a sink; once enough nutrients are removed from the water (which takes a few weeks), lighter colored hair algae usually grows, which can be pulled out by hand.
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