Hi

I just got a fish tank. I have some watercress in bunches. They are
held together by a nonrust-metal wire and are planted into the gravel
in the tank. But the roots keep on rotting. I'm not sure what to do.

Although they are growing new leaves and have grown longer.

Do I just leave them in bunches and let them float around, instead of
planting them into gravel.

Thanks for any help