Well that's good b/c they're the most sensitive to the toxins that leathers release during that phase, but still just the same, I'd run some carbon from time to time just so it can suck up some of those toxins. I no longer trust leather corals of any sort anymore b/c everything could just be perfect in your tank & that same leather can just up & die on you when you're not around, then just like that...TANK CRASH. I once had an unhappy leather that decided to die & nuke my tank while I was gone for 2 days. I lost $650+ worth of SPS & LPS.