Plants are more likely carriers of parasites and snails that might carry disease. Or the parasites might be the fish problem you encountered.
Chlorine bleach dips can get rid of most of these parasites and you can pick off snails but snail eggs might survive. Timing is critical to bleach dips. Low concentration of the bleach will help the plants survive but then you need to do the dip for an extended time. High concentration of bleach will kill the parasites and snails quickly in a short time but probabl also affect the plants. Find out recommended concentrations and times from some group like GWAPA.
I like to use alum, the pickling agent. It is aluminum sulfate and is available in stores for pickling vegetables. So it is safe for humans to consume in small quantities. Use 1 to 3 tablespoon in a gallon of water. Soak the plants in this mix for about an hour, rinse and use the plants. This can be used on plants collected from local ponds and rivers. Use a microscope to look at the stuff that falls of the plants to the bottom of the bucket.
A longer time of a day or two is needed to kill snail eggs with the alum mixture since the eggs must hatch to kill the snails. Probably doing a one hour dip every day for three or four days in a row would be just as effective and less harsh on the plants. Just keep the plants in regular water in a bucket between dips and clean the bucket each time.