Can I put an ivory snail in a one gal?

I would suggest you start out right, with a 5 gallon heated filtered tank. You could keep a single beta in there too.

I betta needs at least a 5 gallon tank.

Bettas are highly tropical fish that require a stable temperature between 78 and 82, 24/7.

All fish require a filter. Without a filter the fish is living in burning ammonia and toxic nitrite.

No fish should ever be removed from its home to do water changes. Any time you touch a fish with hand, net or anything else, it loses slime coat "fish immune system" and it will be open to disease and infection.

Use a gravel vacuum to change 25% of the water once a week for normal maintenance of a cycled tank. Use the vacuum to sift gently through the gravel and remove waste. Add new water that is as close to the temperature of the tank water as possible and has been pre-treated with water conditioner.

It is best to do a fishless cycle before adding fish. cycling a tank takes 4-8 weeks.

Until the tank finishes cycling, 30-40% water changes should be done every 1-3 days.

http://www.fishlore.com/NitrogenCycle.ht...

Feed the betta what it can eat in 2-3 minutes once a day, or 1 minute twice a day. About 3-4 pellets a day.

bettas are carnivores and it is important to offer a variety of foods. A few thawed out frozen blood worms and or brine shrimp1-2 times a week instead of pellets or flakes is important for long term health and happiness.

I found a website. It basically says that one medium ivory snail should have at least 2.5 gallons to itself. Therefore, I would not recommend putting it in a one gallon. Therefore you have a choice:

1. Get a baby snail for the 1 gallon and wait 2 months and then upgrade to a 5 gallon.

2. Get the 5 gallon right away and put a filter (you can house 2 in here).

I recommend the 2nd option, however, I think that you should get a 10 gallon and then put 2 snails and a betta.