[Wet Thumb Forum]-Purification properties of java fern & moss

[JohnArgentina]

You can try some Melanoides snails, they constantly removes the substrate. In my experiences, when i used deep sand substrates or fine gravel, some parts of it turned black (putrefaction). Since i use melanoides, no black spots in the substrate.Another technique : use plants that makes a good job oxygenating the substrate : saggitaria subulata is one example.
Greetings from the South, Juan.-