Hi, I was just wondering about these questions:
How many gallons does a freshwater snail need?
What do they eat?
Can it be kept alone?

Snails need about 2-3 gallons each. They eat algae, algae wafers, cucumbers, zucchini... I have never kept one alone but I am sure it is possible.

I highly recommend against getting one for your current tank as you are already incredibly overstocked. IMHO, you should spend your money on upgrading Nemo and Cynthia's tank instead of setting up a snail tank.

Yes, I was just wondering because I have the old 1.5 gallon setup Nemo used to live in is still usable so I was just thinking...

I wouldn't keep a snail in a 1.5 gallon, they produce a lot of waste. I kept one in a 5 gallon and had to do a lot of water changes.

I kept a pair in a 10 gallon and it was horrible. If I were going to get back into keeping snails I would use a 20 gallon tank with canister filter, keeping only about 5 snails and a few small, friendly tropical fish that could handle the same requirements of the snails. I have always preferred to go with species only tanks tho, so needless to say my last snail tank was snail only.

u could always get a betta instead they have some really nice looking ones

True, but IMHO 1.5gals is a bit tiny for a betta.

Then again, the betta that I bought for Thomas has lived in a 26gal and a 20gal before being permanently transferred to a 10 gal. We spoil him. Still, 1.5 gal will need much more frequent water changes than a 5 or 10gal.

I always did daily 100% water changed when I kept them in anything smaller than 2 gallons and every other day 100% changes when they are in anything between 2 and 5 gallons that is not filtered. Horatio lives in a 5 gallon filtered, so he gets water changes depending on the test results.

Just though I would throw this in, my snail absolutly love tubifex worms. I buy the OmegaOne kind that you stick to the tank. I usually put one right in front of him and he will cover it up and eat the entire thing. Then he will try and get to the other ones I put in for the fish. I have seen him eat 2 1/2 cubes. I think my goldies have figured him out though, now they just rip them off the glass so Mr Piggy don'e eat them all. Cories love them too.