Hmm.You didnt say if the algae is in an outside pond or indoors in a fish tank. I don't have a pond, but I do have a coldwater tank inside with just goldfish. When I change their water I just scrub off the algae with a cloth and plain water,It comes off easily. I was told by a fish breeder to leave a little algae there. It may not look so pretty, but goldfish actually like to nibble at it, it's food for them.
By
08/21/2006
You don't say what the green algae is on. But for most purposes plain old laundry bleach will kill it.