How do you know when the water has cycled?!!
Ammonia and nitrite will go up in levels. At that point if you put in snails they will die. They can not handle the spike. Wait until the nitrite is down. Wait until your cycle is done. It's only been 4 days sinse you set it up. Wait at least 4 weeks. That's an estimate when the cycle will be done. IMO.
Also, do not put any fish in there either, they will die.
Sorry for losing it, but this is the crittlical time when you need to wait. Don't rush.
I would start with 1 hermit and different types of snails. maybe 4 of each. Nass, certh, ..... my mind went blank, bedtime.:sleepy: