Getting black sour hip bath mixing bowl? Ok, long story short - my room mate is a slob and...

Ok, long story short - my room mate is a slob and never kept the 2nd bathroom clean.. I had no concept until the other day when I looked in nearby and was mortified! Its probably been a honest 6 months since it's seen a cleaning product. I have be trying for about 2 days now to bring it clean, bleach, Comet, Easy-Off Bam, scour pads, everything.. I even moved out bleach sitting on it for 2 hours. Is there any secret trick to getting the black past its sell-by date? Any suggestions? I really don't want to have the entire tub replaced, so if anyone has any direction I would appreciate it soooo much. Thanks!
Answers:    try the WORKS but,,..spray it on instead of pouring..also..westleys bleach white white wall tire cleaner is very good...capture em both at the dollar store..good luck
Mr. Clean Magic Eraser-gets really tough stains out
Scrub brushes

I usually use Comet(powder form) but since its not working for you i would try soft scrub