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Alum. Is it safe for Fish?

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I have a tank. It's milky white. Over a week. Nothing was working. Moved the fish yesterday, and thought I'd just use it to quarantine plants for now. Dumped in the plants. Added Alum. Checked on them this morning. Tank water is crystal clear. Crystal. I mean, I have to test the parameters, etc, but wow. I want to add some to the other tank now, to see. 


Anyone know anything about this?

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I've heard of uses with alum being used in ponds/lakes as water treatment but would err toward caution and not using it, especially since your intended function is cosmetic treatment. White clouding is usually a bacterial bloom that sorts itself out in a few days/weeks and when I get one I usually let it run its course.

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Agree with ange - Alum itself is a flocculant, that is how it clears water so quickly. It causes particulates in the water to aggregate and sink to the bottom, creating a crystal clear water column. It's used industrially and to treat polluted bodies of water/swimming pools.

I've read on nat geo I think that aluminum sulfate (alum) can be toxic to animals after a body of water is treated and the animals consume the water. I believe it is the aluminum part that would be harmful to fish as it's even harmful to humans in enough quantity.

Hoping someone on here has some applied knowledge - but, I personally would err on the side of caution too. 

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