With 99% humidity, a 3 month prolonged rain season with 3-5 hours pouring buckets only sand would drain out. The problem is Cyanobacteria, I hit it with a dose of Amoxelin, two tablets of half a liter, two spats a day. It stopped the next day. The blue alge or Cyanobacteria, is all over the trees, concrete, walls and anything exposed. We hardly have dry days. One of the longest rain seasons that I have seen in 26 years. I have taken all my Bonsai's and used the pressure cleaner to clean trunks and branches. The was some loss of leaves, but that does not worry me a bit. Tropical climate has its own chalanges. I went through all on moss Google had to over, but it did not help. The smell gave it away. I used to have large tanks the Cyanobacteria was mostly a problem when the nutrition where to rich. Antibiotics help. Problem solved, will take pictures and post when I get to it. Thanks for replying!