ARGOS® This rapid response, contact algaecide is a liquid, copper-based formula used in ponds and lakes to defend against floating and submersed algae.  It is effective in a wide range of water quality conditions, including hard water systems. Treatment results for planktonic algae are noticeable in 24 to 48 hours and filamentous algae in three to four days. When used as labeled, water treated with Argos has no water use restrictions