What in the world do you mean minimum of 5?
5 Loaches? Oh. lol. If you want 5 coolies in a 13 gallon tank, you'd have no room for the Bettas. MTS are Malaysian trumpet snails, often called a 'pest'.
Very peculiar, many of the ornamental snails are horrible in planted tanks... Apple, mystery, all are pretty likely to devour your plants. Nerites are ornamental, don't breed in freshwater, and are great though.
The pest snails that people hate, (ramshorns, pond, and MTS) are actually the best cleanup crew you can have. I would email a company that specialises in plants (Aquarium Plants Pond Plants From Sweet Aquatics
) and if you order some plants they'll include some snails for free.
Pet stores will usually treat their aquariums and kill the pest snails. You can also try ebay or aquabid.