Would these sponges be safe for cleaning my tank? They are advertise as "natural" but i noticed they are made with agave fibers. Would this be toxic? Not to worried about using them. I just had a few extras laying around. https://dteps.3dcartstores.com/mobi...uJsjq8mMc5OWzOKZjgVYxU0XZKDZQ9t8SghoCHuXw_wcB