im absolutely sure this was not damaged due to fish. i started seeing it after it started growing extremely fast(which coincided with the date i added aragonite). i put a single stem in another tank when i got it, which has not shown the splitting and has only grown about half an inch. the trimmings from one tank are already longer than the single stem, which i keep in a more conventional tank.
these are the clippings from just the last week. i clip about 3-5 inches off of the stems when i trim them. you can see which ones i planted last week and which ones i planted today. it grows fast.