That's your filtration. Your tank needs to be cycled to grow the bacteria that will convert the waste from your fish into less/non toxic compounds. I'll post some links or you can search here or google 'saltwater aquarium cycle'.
For the short term don't worry about your ph. When you cycle it will vary all over the place until it's done. Even then 7.8 is fine. Your fish will prefer stable ph over a specific number (within reason).
You've got a long way to go before you can add fish. Ask the questions you have and someone here will add their 2 cents. Keep in mind that it's the posters opinions. In the end you need to do your own research, weigh the opinions you get and make your own decisions. It's your tank, your money,blah blah blah.
Also, post in the saltwater forums (Getting started), more people peruse there than the local forums.
and BTW: Welcome
Fishless Cycling For Dummies