I use Turface as substrate in one of my tanks. Some of the grains are turning bright blue! Not blue-grey, but really blue. I have used an Ich treatment lately, but can't recall if it was there before. It is affecting some grains, and not others, which are still tan. I would figure if it were staining from the treatment, it would affect them all, right? It also seems to only be affecting grains on the surface, not the ones underneath.
Anyway, has anyone else heard of this? I'm rather perplexed.