I cleared my tank of snails. I sold everything and got a new tank. On a more serious note, I tried a range of things - harvesting with/without traps of various kinds and veges in the tank but if your water is too soft to add snail rid then I think you can kiss goodbye to any chemical fix-alls.
If you don't want to buy new fish to eat the snails and you have a spare tank you could move all your fish into it, snail rid the tank to all hell and back, change the water 8 billion times and then move them back in.... that would work but it's a lot of effort and probably easier to move the fish into the new tank and then clean out the snail tank.
In my new tank I snail ridded almost all the plants that moved in, washed others by hand under the tap and so far I've only ever found and caught 2 ramshorns. Have had the filter out frequently and never find any eggs, which was Snail HQ in previous tank. I think and hope I am currently snail free. (touch wood & fingers crossed)