Bettas and cories?
 

I'm going to be upgrading my betta from a 2.5g tank to a 10g tank, and I would like to get some other fish for it. Would a corie of some sort be okay? If so what kind of care do they need?

Pygmy cories would be a nice addition to a 10 gallon tank. Most bettas do fine with them. They should be kept in a group of at least 4 though - 6 would be better. I think you could keep 6 pygmys and a betta in a 10 gallon if you're good with upkeep and water changes.

I am almost obsessive with keeping my tank clean so that's not a problem. What kind of food do they need? Also, do they get very big?

They only get about 1.5". They will need a sinking pellet, or maybe a small wafer would work. Mine also liked bloodworms (frozen or live).

Well I already have the bloodworms for my betta, so that's easy enough. They are bottom dwellers then I take it? Will they be okay with the coarse gravel I have?

They're bottom dwellers yep.

They prefer a sandy substrate, but as long as your gravel is smooth there shouldn't be any problems.

Also, pgymies can be hard to get a hold of depending on your area. you could also look into kuhlies, or otos.

Another cory about the same size is habrosus. They also get to less than 1.5 inches and are sometimes easier to find. Care is about the same.

Okay, I will have to go see whats at the local pet store, I'm also lucky that there is an actual fish store not far from me. I'll have to see what they have and report back.

I have some left over gravel from when I made up my betta tank, but I was actually thinking about going with sand for this tank. I don't know if that would stress my filter or not though.

I've got sand, and I haven't had too many issues with the filter. Just make sure you rinse it like MAD before adding it. My cories used to be on gravel, which I thought would be ok, since it was smooth, but since switching to sand they are SO much happier. Their barbs have grown really long and they're much more active. I'd definitely recommend sand for cories- they're awesome, easy fish to keep though!