What Is The Brown Sludge In My Toilet Tank?

What Is The Brown Sludge In My Toilet Tank? When Iron Bacteria “feed” on iron in water, the dissolved “ferrous iron” reacts with oxygen in the air to form rust-colored iron oxides (ferric iron). … If you see slimy or clumpy deposits, they are likely caused by Iron Bacteria. Iron Bacteria Slime in Toilets. Orange/brown/red