would it be ok not to feed for 9 days?

hmm.. Do you know of other small hardy fish that will do good in my aquarium?

I want to add a betta later on, but I wanted to have maybe 1 or 2 more companions.

what about the Glo fish they sell in Live aquaria?

 

I would only have a betta, a 3 gallon tank can't support a large bioload at all. And tetras are schooling fish, they do better in larger tanks IME

 

glofish = 10g or larger for the necessary 5-6 you need for them to be happy. with a 3g setup, you're basically limited to a betta. Not the worst thing in the world though.

 

This is absolutely sound advice.Neon tetras get a disease that is called yep you guessed it."Neon disease".There is no known cure and it usually ends up killing most and can happen quickly or slowly.(Sometimes even after a year)Cardinal Tetras are not suseptible to this disease and are IMO better looking.(The difference is the red stripe runs to the tail instead of halway down the body)
With all that said I do think your tank is a little too small for these particular Tetras.If you are planning a Betta I would probably stay away from Glofish as they are basically Danio's which can be fin nippers. If it were me I would probably just add the Betta.
IMO I would not start over but instead run some carbon and or a Polypad to ensure you didn't introduce any harmfull chemicals.

 

Just go with a Betta. There really isn't much you can add to a two gallon tank.

 

You could always make it a Cherry Shrimp tank

 

I was actually going to suggest adding something like an amano shrimp, but for some reason I thought it'd get too big, not sure why. But yeah, cherry shrimp are pretty cool too, if you want that instead then go for it.

 

A Betta and a shrimp is not going to work unfortunately.Bettas love shrimp.To eat that is.

 

A betta can eat an amano shrimp?!

 

How are you getting oxygen into there other than the plants?