Although emanwols is correct, if you want to solder the two together, then there are a number of ways of doing it;
You can use any method if you make sure that the joint does not touch the water, but there are those on the forum who feel that it is better to be certain about not letting the joint even become wet, and there is nothing wrong with being certain.
1) Use emanwols method and hammer the anode to the suspension wire, like riveting the joint.
2) If you want to solder the joint, it is possible to buy solder
https://www.cooksongold.com/Solders/-Alloy=Silver_Solder/-Type=0/&prdsearch=y which is cerified as resulting in a joint which is .999 fine, like the two components. Jewellers must use these grades of solder, or their finished piece is not allowed to be hallmarked as pure silver, so this is a way round the problem.
3) Choose another method of suspending the anode from the electrode holder; some people have suggested pushing the anode through a plastic plate, others use a pair of plastic plates which grip the anode securely with an independent elecrical contact clipped to an area of the anode which is so far out of the water that it will remain dry.
If you want to be certain,