Hello. I too have these crabs. Had 3 males and one female. Now 1 male and 1 huge female. Had them in my 75 gallon but after a week they killed 2 horseshoe crabs. On top of my dead horseshoe crabs they literally were ripping the spines off my pencil urchin . It took a long time untangling them to try to save my urchin!!! This all happened at 2:30a.m. thank God my dog woke me up or my urchin would've been dead too. I took water outta 75 and a rock and put crabs in a 10 gallon with heater and filter. Thay are still in there (only 2 left. I lost many animals due to that hurricane that came through Tennessee). The next morning I noticed my pink cucumber was missing in 75. I found it, dead. It had chunks out of its body. Like pincher chunks. I'm sure those crabs got cucumber 1st. I'm so thankful it didn't nuke my whole tank. Just be very cautious

about these crabs