So just an update -
The tank is cleaned out, and the background removed with a razor.
Im bumping this thread up so that Hydrophyte can see the tank - he is going to help me make the drop in feature.
The circles are rocks, blue line across is approximate water level.
You can see a crudely drawn drop in manzanita feature, and the green squares are planters that will be built into the great stuff background.
The rocks will have those very small plastic coral cuttings and barnacles on them.
Let me know what you all think.