I am currently in the planning process of my seahorse biocube and love the idea of black sand as its stated to make the colors of the seahorses more vibrant and stand out. However, looking into it more it seems that it contains lots of iron which is toxic to fish and corals. The tank will be mostly macro algae and some gorgonians down the line, along with 1 pair of seahorses and MAYBE a goby for the uneaten food. Is black sand really that bad for fish as I do not want to set up the tank and then kill the seahorses in 1 go