Hi Lurker,
Funny username! And as my username may suggest, I have been breeding both Ramshorn and pond snails for my Figure 8 and Dwarf Puffers for almost a year now so may be of some help to you.
I have 2-10 gallon tanks for Ramshorns, and a 5 gallon for pond snails, though there are also a million pond snails in my community tank as well (not on purpose!) Both of these snails breed very quickly if they are fed regularly and the tank water is at least 78 degrees. Ramshorns grow much faster than pond snails, so fast in fact, that I had to set up an additional tank for them and still have to regularly cull out the ones that are too large for my F8 to eat and either bring them to my LFS or put them in local ponds!
The most important piece of advice I can relay about pond snails is this: Baby snails tend to stay under the gravel most of the time where you can't see them, hence you will end up with many more in your tank than you think you have just by looking. I discover this every time I vacuum the gravel (always check your bucket before chucking the water, as there will likely be a hundred tiny snails you might otherwise discard.) Believe me, it will get to the point when you will consider either setting up additional tanks or chucking the ones you suck up (or maybe sell them!)
It will take a little while, several months, to get large numbers like this however, mostly because they really do hatch and grow slowly. But they are CONSTANTLY laying eggs all over everything. The eggs can be hard to see, but they're there.
As your question is whether you will have enough snails to feed your F8 on a daily basis, my answer is: Eventually. It really depends on how many you're starting with and whether you have at least 80-100 that are big enough to provide a meal for the Puffer until the babies grow to feed-able size. This is why I started with Ramshorns as well, because I had the same concern, and I'm glad I did even though I have too many of both kinds of snails now. Honestly, patience is not one of my stronger traits
If you have the patience to wait for your initial batch to get their shop set up, you can supplement your F8 with frozen shrimp, bloodworms, clams etc. I actually feed my Puffers these other foods as often as I feed them snails (another reason why I have too many snails!) Or you can get your hands on a couple of Ramshorns and then stand back and watch your farm runneth over!
A word of caution about keeping Ramshorns and Pond snails is the same tank: The Ramshorns will eat the Pond snails' eggs. They will even eat the eggs laid by other Ramshorns! That used to bother me until I had a large enough number, now I'm happy about that
Hope this helps! If you have any more questions that I can answer, I would be happy to share what I have learned so far. Raising snails is a pretty fun thing for me, and has added to my enjoyment of the fishkeeping hobby in general. They are fascinating to watch all on their own!