You can get a path and patio weedkiller spray, usually containing glyphosate that takes the poison gown to the roots, takes a few days to work and needs to be sprayed on weeds that are actively growing.
Do take care to follow the instructions on the bottle and to keep it away from other plants, lawn edges garden ponds etc.

Nothing wrong with using roundup in ponds pam....i use it all the time in fully stocked ponds to kill bullrushes, lillies and water hawthorn. Very effective.

Do you Andy, I didn't know that, just thought better to be safe than sorry.......

Not much use putting glyphosate on after the weeds have been removed though as it works by translocating the stuff to the roots. If there's no danger of runoff onto beds you can use Pathclear, meant for the job.

Thank you, it sounds as though Pathclear may do the job.

I would not use Roundup anywhere near ponds. It is highly toxic to amphibians. Monsanto, who make Roundup, have conducted their own study, and have concluded that it will kill tadpoles, and the adult frogs and toads. It is widely used in ponds, and large bodies of water to control rampant weed growth and, as Andy suggests, works well. However, from my angle as conservationist and speaker to many organisations on wildlife gardening and ponds (as a stand alone subject), I would advise against it