Vinegar will bring your PH down, so scratch that idea. Baking soda will work in an emergency, but I don't recommend using it all the time because it's loaded with salts, and you'll need to flush periodically to avoid problems. I've been using PH UP(API brand) for aquariums, and it works great. I ordered some Technoflora PH up, made for growing, and plan to switch to that as soon as it arrives. But, if you want to use the aquarium stuff, it will do the job without any problems. I chose to go with Technoflora, because I'm a perfectionist.

(also, they use a different chemical to adjust the PH, which is aimed towards better plant growth)
Just make sure it doesn't contain any phosphates. API is a common brand, so pick that up if they have it, and you'll be good to go.