The Blue Sponge is a filter-feeding sponge, not a true coral, with a vivid blue-to-violet color. Many blue sponges host photosynthetic bacteria, so they get energy from light as well as from filtering the water. Picture 1 is under white light; picture 2 is under blue light.
Why We're Obsessed
That blue is almost unreal in person, and there's not much else in the hobby that color.
Care: Moderate light and flow. Never expose it to air; trapped air can kill a sponge. Best in a mature tank.
