Do you know that Rasool Allah has cursed those who have tattos? لَعَنَ رَسُولُ اللَّهِ صلى الله عليه وسلم الْوَاصِلَةَ وَالْمُسْتَوْصِلَةَ وَالْوَاشِمَةَ وَالْمُسْتَوْشِمَةَ -ابو داود Don't know about the Ghusl. If the tatoo is over the skin then ghusl won't valid otherwise it will be.