I've tried the weldbond/cocofiber method for creating a land area in a newt tank, and the results were a complete failure. The structure was dried for two weeks before being completely submerged in water. It did hold together but constantly leached fine particles into the water, thus water was never clear. Minnows for cycling the tank could live in the water, but a brave newt sent in to test the water exited before not to long and the whole setup was scrapped.
In a dart tank I have been putting together, I used the weldbond/cocofiber method. In an area where some water will trickle over the weldbond/cocofiber, I added extra coats of 50/50 weldbond to water, in hopes of really sealing the structure. It has been drying now for a couple months, and soon I’ll give the water feature a test run to see how it holds up. I’m hoping to avoid any rehydration issues, but we’ll see.
Will