Getting started...

If you have chlorine treated water, then allowing it to sit overnight will gas off the chlorine. If you have chloramine treated water, you will need to use a treatment such as Amquel. Letting the water sit overnight will also gas off any CO2, and will get it to it's 'real' pH. However, there may be no need to adjust the pH, depending on your results. The varies chemical choices usually come with unintended consequences (ie, phosphates that create an algae buffet), so are discouraged. The tetras will prefer softer water, but can be acclimated to harder water with a little patience on your part. Acclimating the fish is a better alternative than treatment. So, unless your pH is above 8.0, I wouldn't mess with it.

Once the water is clear of chlorine/chloramine, you can begin the fishless cycling process immediately. No reason to wait!

For a cory recommendation, I am very partial to the skunks. They won't get as big as many species, have lovely coloration, and are good socializers--they'll be thrilled in a group of 4-5.

most tapwater's pH is near enough neutral, which will suit the fish you have chosen, so i wouldn't worry about changing it. leave the tank so cycle for afew weeks, keeping an eye on nitrite, nitrate and ammonia levels, and once these have finally settled you can start stocking your tank, slowly at first no more than an inch to the gallon, then increasing your stocking to 2 inch to the gallon (if you want...no law saying you hav to. lol). i would recommend corydoras julli, the leopard cory, as it is my personal favourite.

hope this helps.

Check out my Getting started page for more help on starting a new tank.

I agree, don't alter your Ph unless it is well over 8. I have a 29Gallon aquarium with the Ph right around 8.2, and I haven't lost a fish yet (6 Months)

As far as what Cory to get, I love the Albino's, very active and love to play with each other. They also do an excellent job of cleaning the bottom. I have 3 Albino's in my aquarium and they are my favorite.