THREE times a day?!?! That's way too much. I feed my tank once a day, most days. I feed about 5 times a week. Overfeeding is the root of the problem. Less food means less snails. The fish will find the food much sooner than the snails, but if you are overfeeding the fish, they are far less interested in the food and the snails will find it, and repopulate quickly.
Starve the tank for about 3 days (the fish will be just fine), and then you can start to make inroads. Honestly, there's no "quick" solution that won't cause more problems than it will solve. Don't overfeed and the snails will be a "nuisance" not a swarm.