The algae most commonly available for sumps is Caulerpa prolifera which in my experience will not grow if you have ammonia, nitrites or high nitrates. Also in my experience, it will not take root in Miracle Mud! It much prefers coralline sand and attaching to live rocks. Again in my experience it needs fairly intense yellow/white light and low flow.
Since your tank is only a week old, you probably have peak ammonia production and rising nitrite levels at the moment, so in my experience, no don't add macro algae to your sump yet.
Start testing your ammonia, nitrite and nitrate in another week and see where they are.
