What you've got there looks like a boat's lifetime of mold and dirt. Another way to clean it is with first, a good wash (from the garden sprayer, with a solution of water
, dishwashing detergent, like Dawn or Joy, and household bleach. Then follow up with a wash of clove oil
(Google it.) The clove oil
is good because it will penetrate into the pores where the mold organisms have established themselves and kill them.
Still, you're in Florida
, and the mold spores are in the air, so expect it to return.
I am not familiar with concrobium, it may work as well as my idea, just no data to compare methods.