It depends on the plant species. Rhizome plants take it best, stem plants are more sensitive.
I've used 19parts water to 1part bleach, then adjust my 'dip' times according to the type of plant. Then you have to rinse like crazy (just tapwater initially), then soak plants in a buck of dechlorinated water with 5x the dose of dechlor.
Sadly, there is always a chance of killing the plants with the treatment.
Some just rinse the plants well in a bucket of dechlorinated water and then put the plants and enough water to cover them in a plastic bag that is completely dark (black garbage bags work well). Then leave them in there, tied shut, no light at all, for a week, and see what survives.
Cyanobacteria is nasty and hard to get rid of. Until I ordered the plants from an online source (who has refused to refund my money but instead wants to replace the plants ~but no way am I going to go through all that again~), I've never experienced it. And I've been keeping planted tanks since the mid 70s.