WOW. nice job.
Im not sure that 2.5g is going to be large enough. Maybe right now. BUT that is alot of snails and very little surface area for all of them to cruise around on. Id go pick up a 10g at the LEAST to put them in.
You could also post them for sale to thin out the herd.
Id buy a couple.
There are 2 types of people on this forum. Those that have algae, and those that lie and say they don't.