What about invertabras? I noticed a couple of hermit crabs and an emerald crab die over the past 6 months, thought it might just be coincidence, but then read I should be adding some kind of kalk for invertabra? BTW my alk. was low, could it just be low alk. our is there 2 kinds of alk. additives, one for coral and color, and one for inverts.?