Well, reducing the flow through the valve did the trick, however, I will still install the elbow as I think I need to reduce the splashing. The vaporization rate is quite high, I'm topping up daily with about 4-5 litters, is that normal?!
Another thing, I have just found a yellowish green fuzz on the glass, tubes, and in the sand, below are some pictures. Any idea what would that be?
My tests are all zeros and there are 4 chromis damsels, one royal gramma, 2 peppermint and a bunch of snails.