How do I get rid of black gunk in my drains?

In all my drains in my house, there is this black slime nastiness accumulating on the inside. Is it mildew? I scrub the black off the inside of the drain plugs with a toothbrush and it comes up. Two weeks later when I go to clean it again, more black has 'grown' in. It also forms on the drain holes in my shower. My house is only 4 years old. Unfortunately, I cannot remove my drain plugs from my sink, at least I don't know how.|||There is nothing you can do about the black slime. I forget what it is called (has a fancy scientific name) but it is basically a fairly safe bacterial slurry. It feeds off of some of the ingredients in soap and organic matter. If you ever open up a pump pit that pumps strictly laundry water there are usually massive amounts of the stuff. Hard to wash off skin too. May not have to embrace it but living with it you will have to do.|||I use Bam Bathroom Cleaner,it not only cleans tubs,sinks,and tolilets,but you can also pour it down the drains and it keeps them clean and unclogged.|||Use a bottle brush.