I'm thinking about culturing snails to feed my fish, which snail should I culture?

Which fish? A lot of smaller fish won't be interested in snails ...

To echo cathies comment, which snail eating fish do you have?

Snail eaters have different needs depending on shell thickness - some are more 'crunchy' than others lol - so can damage the mouth parts or cause injury.

I don't know what fish is it. It's some kind of salt water puffer. I don't keep them but my dad does.
He used to have a marine tank that keep only puffer which we caught and vacation... but after a few months, they died cause short of food. We had no knowledge on these fish and they refuse to eat fish food we bought, they only eat snails (I discovered this by dropping a snail in the tank for fun, that snail was crawling near the tank).

After seeing him bought a new tank and some sea salt... I asked and he said he will do it again next vacation

This might help:

http://www.wetwebmedia.com/ca/volume_6/volume_6_2/puffers.htm

The puffer he was keeping was different! Although we caught these too but I didn't like the look of it so I released them. The puffer he was keeping was like yellow with black dot on it

I thought it would be helpful for feeding recommendations though as they are common to all marine pufferfish

It is, thanks... sorry but I only get it with the third time xD However still... which snail is the best, I can't always feed them with shrimp or squid? i've searched and found the puffer my dad going to keep is green spotted puffer (it's not green, it's yellow LOL!!!)

Ah they are brackish not marine profile so any freshwater snails, whichever breed quickest, not sure which they would be locally to you. A puffer that size should be able to tackle malaysian trumpet snails, they multiply very quickly with plenty of food.