[Snappy]

8-10 inches, yikes. For those size sweepers do you know which type of hydnophora? Angyak, what kind are we talking about that you want to get? There are several species so I think it might be helpful to be specific. I have a few hydnophora rigida in my tank and yes they are aggressive but IME a 3" seperation is all that's necessary, unless your flow is blowing in one direction (which it shouldn't be anyway). But yes be careful of the "spiderweb" on less aggressive species. That said, I actually moved my largest colony into my refugium because my hammer was killing it, so they don't win every battle. My tank is pretty packed and doing quite well so I am not sure I buy into the "don't keep them in the same tank theory." However in my reef I also have some LPS & softies so I run carbon to help control all the chemical warfare, so yeah I guess I would recommend if you keep hydnophora with other sps you should run carbon.