That's what I've read, that they are medicated. I've been putting one in the tank every 6 weeks or so. They only last about a week before they completely desolve. Problem though... Mike thinks it's food so nibbles on it if I don't hide it well. I think it's unfortunate that the turtle conditioner and cuttlebone are the same color (white) because Mike really does get confused easily.
I didn't realize that he could grow immune to things so I guess I'll cut back some of the conditioner. I watch my turtle constantly for any abnormal behavior (based on what I've read on the forum that is considered weird for turtle-kind).
I have algae clearing drops for algae. I'm not being overrun with algae as much now that I've reduced substrate in the tank. And the water-conditioner works I guess. At least my turtle doesn't act funny (okay, he's funny but only in a cute way) about the water and his eyes and whatever.
>>If I am correct, the blocks are mildly medicated and are useful if your turtle is under the weather with illness, etc. I really haven't heard anything bad about them. Some recommend that you not use them on a regular basis and only if the turtle needs it. There might be a possibility of the turtle developing a tolerance for the beneficial "stuff" in the block that helps clean, condition, and fight yuckies. So many use it as an occassional, medicinal thing, not like bottles of "water conditioner" that remove chlorine and irritants from tap water.
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>>To the best of my knowledge they don't do anything against alge.