PLANT UPDATE
Really happy with plant growth under this very low-tech setup full of water-goats.
Anubias roots are being nibbled but not excessively - I can see the roots working their way into the groves and crevices of the wood already too. Congensis anubias is thriving, short and sharp anubias is more just-surviving.
Java moss is already slowly spreading and standing up towards to the light. The humidity keeps it perfectly moist. Hopefully it will root itself down in time.
The salvinia is not being touched by the SD's from what I can see. It looks like it's spreading out by about 1cm per day with each plantlet gaining more leaves. My aim is for it to cover the back and centre surface (between islands 2 and 3) where the filter ripples meet.
The air plants don't appear to be rotting in the humidity - with thanks for the humid tolerant species suggestions.