Sorry for the late reply. I am out of the town most of the time now, so I have to rely on my parents to take care of them. There are some changes done to the tanks since I saw them last, and I don't have the latest picture. The last update that I received is that there are 3 tanks placed side by side on the floor now:
The left and middle tanks are the old ones (1m x 0.6m x 0.6m) which are linked by a bridge. The left tank contains sand, while the middle tank is inhabited by the female RES. The right tank, roughly 0.5m x 0.6m x 0.6m, is occupied by the male RES. It is a separate tank by itself. We placed a piece of board in between of middle and right tank, so they can't see each other.
In the right tank, the male RES is really, really restless. He tries desperately to climb over to the other side, and jumps around when he spots a human being, asking to be moved back. I guess he is trying to show dominance, and he wants to return to the bigger tank with a nicer basking spot.
The female RES is still scared of water. We tried to put her in the water to show that the male RES is no longer around, but she will panic and desperately trying to get out of water. When she is back in the basking spot at the bridge, she occasionally glances into the water or into the sand tank. Seems like she is worried that the male RES will pop out from nowhere and attack her again. She hides her tail whenever someone approaches and does not go down for a drink until we force her to go into the water for feeding.
We also have a bottom feeder fish in the middle tank. They grew up and lived together for at least 3 years now, but ever since that incident, she is scared of the fish too. Basically, she treats water like a poison now. I think it will take quite some time for her to be back to normal.
I wonder if they can still communicate with each other in this new setup, hence causing distress on the female RES?
By the way, could you recommend any good tank filter for floor tank? I have tried internal and external canister filter, but they spoil very easily due to the sand in the water. Removing the sand from the water is difficult since the female RES always bring some sand back from the neighboring tank.. Thanks!

