First i cover with fabric or 8 oz NON WOVEN GEOTEXTILE. Fabric Is way overlooked and underrated. Why? When you have exposed liner there's not much you can do with it . Wait for bio film let it grow on it and in the mean time let it age in the sun ?
Fabric as I'll call it, what I buy is polypropylene and I have pulled pieces out of the ground that had been burried there 30 years and no sigh what so ever of falling appart or rotting.
I cover everything in the pond with fabric. So the lengthy answer is yes fabric and then mostly rock ,or wood ,moss and bark. Maybe something like hens and chick's cut in where it's root are tucked in a slit. A couple times I put dirt down on the liner then sandwiched it with fabric and let plants grow in it to create a natural looking growth of plants right to the waters edge.
Some call it weed barrier, to me there is little that can stop mother nature. Except nature it's self. This pic looked great the other night but we had a racoon stop by and he found the area had something for him and ripped it appart. It was just fabric liner fabric and plants on cinderblock.