last attempt was six months ago. I didn't need to patch in photoshop this time, but it did take some effort to get decent pictures.
This is what it took: I put towels on the floor and bed, got a two-gallon bucket and dipped out most of the duckweed w/a bit of water. Lifted off the light strip and laid the panes of the lid aside. Blocked window light- that took some doing. Just pulling the curtains was no good- still had glare on each end of the tank. I tried several things, ended up taping black trash bags over the top half of the window and leaning huge sheets of cardboard over the bottom half. Got up on a stepstool to get all the tank in the frame. Tried several different settings on the camera to find the one with the best color and light balance. Messed around with desktop lamps to get the lighting right- I ended up putting one on each side of the tank, slightly overhead.
All this with the filter turned off so the water wouldn't be moving- the current is very slight, but even so it makes a blurry image. Oliver hid the entire time, so I didn't want to distress him too much. I only worked as long as it took to get two or three decent pictures, then plugged the filter back in and put everything back in place. As soon as I was done returning the duckweed ceiling, Oliver came drifting up from his hidey-hole.
I want to do this with the thirty-eight as well, it's so different now. But I don't feel like it yet- maybe tomorrow.