It seems that the "dirt" part of my creation is no longer holding out the water - it is soggy. I have emptied the "smelly" soggy dirt, dried and cleaned the cavity, and now sprayed it with leak stop, while it is still in the tank.
The dragonfly nymps are still swimming around in the water part. I have added a couple of ivy clippings to my pots and rafts to see it they will root.
I hope that tomorrow I can refill the land with dirt, add some plants this week, then in the next couple add crabs.