Correct me if I am wrong however from what I have been reading on ONLY this product it claims to be safe for the filter bed so I would say it would be fine but I could be wrong. I use a skimmer and have live sand myself and thats one thing that stuck out to me was it said... "It does not damage the filter bed."
This is from the product...
SeaChem Cupramine ™ effectively eradicates ectoparasite of both freshwater and marine fish. It has all the advantages of copper sulfate and chelated copper, but not the disadvantages. Like copper sulfate, it is fully ionic and effective at low concentrations. The cupric (Cu+2) charge is fully active. Like chelates, it is safe for fish and is not precipitated in the filter bed. Unlike both, there is more than a 4x concentration gap between the minimal therpeutic dose and the toxic dose. Unlike copper salts, it is stable in the aquarium, and, unlike chelates, it is easily removed by chemical filtration. Unlike other copper products, it is both highly effective and safe in freshwater as well as marine water. It does not damage the filter bed. Cupramine™ contains 10,000 mg/L of copper and 100 mL treats over 500 gallons. Do not use in conjuction with ParaGuard™. Test for copper with our MultTest: Copper™ kit. Marine or freshwater use.
Caution: Turn off your UV sterilizer while treating with Cupramine. UV will break up the ionic bond in Cuprimine; causing it to be much more toxic