Most snail problems stem from overfeeding/over abundance of food for the snails. I see you're doing a fishless cycle - are you doing this with ammonia or a different method? Have you had any algae problems?
I have "pest" snails in my tank. As long as I keep up on maintenance and don't overfeed, their population stays at a normal level. If I slack on a water change or overfeed, I can see more of them appear and I know I need to up my maintenance/feed less. I appreciate them for that, as they are a good way for me to gauge the healthiness of my tank.
You say you're removing them manually - as in picking them out by hand? If you google how to make a snail trap, it's quite easy and effective. You just take a water bottle, snip off the top and place a piece of cucumber or other vegetable inside, then replace the top piece but inverted. Place it in the tank at night when you turn the lights off, then take it out in the morning and dispose of the snails.
ETA: Your tank is gorgeous!
