Bad Pictures Some of the latest frags growing out. I have seen these put on 1/4"+ in a week, no joke. Latin Name: hydnophora rigida AKA: Horn Coral, Knob Coral, Velvet Horn Coral or Branch Coral Phylum: Cnidaria Family: Merulinidae Origin: The Indo-Pacific ocean, Eastern Africa, Fiji/Tonga, Solomon Islands and the Great Barrier Reef Reef Safe: Despite the look it is NOT a true SPS and is extremely agressive. Hydnophora has a VERY potent sting and will kill any corals it comes in contact with. Give it plenty of room to grow. Lighting: Needs high lighting. Should be kept under at least T5's if not metal halide relatively high in the tank. Water Conditions: SG of 1.023-1.024, pH of 8.4. Needs good(440-480ppm) calcium levels and very low nitrate levels to thrive. Flow: High intermittent flow is preferred. Should not be constantly buffeted. Feeding: Gathers most of its need from zooxanthellae but will filter feed and consume zooplankton. Appearance: Flat clustering branches. Tends to grow very densely with many knobby protrusions. Usually shades of green or yellow, with brown specimens tending to be unhealthy. Some of the green specimens will fluoresce brightly under bluer lighting and actinics. Nice specimens are breathtaking under the right spectrum. It should be noted that despite the look this is NOT a "true" SPS, it is actually falls in the LPS category. Growth: Hydnophora is a VERY quick grower under good conditions. Be prepared to frag it often. I have fragged off large sections only to see it growing over the cut areas and starting to rebranch in less then a week. Personal Observations: Very neat, realtively hardy coral. Great for people who want to take a first dive into SPS corals without many of the headaches that come with Acropora. As I mentioned they grow EXTREMELY fast, plan accordingly or be prepared to loose corals. I have noticed it completely grow over fragged areas in less then a week. When adding to your tank make sure it is well secured and can't fall on any neighboring corals, I learned that lesson the hard way. The difference between my two tanks lighting(one is 14k halide, the other 20k) is night and day. Under the bluer lighting it glows a bright vivid neon green.