No, it's not necessary to install anti-malware next to the antivirus. Most antivirus solutions have a built-in anti-malware module that protects you in case something bad is encountered. However, you can never be sure, but if you keen on having two products installed that are somehow connected, then I recommend installing Malwarebytes Anti-Malware. You can find additional details about it through the application's page at Software Informer.