New Tank Cycle causing drop in Alk?

[MadTownFess]

Does a tank consume alkalinity as it cycles for the first time? My goal is to run Alk at 9.0 dkH...my initial saltwater was at that reading. After about 1.5 weeks the Alk dropped to 7.2. I then dosed sodium bicarbonate over a few days to get it back to 8.6. Just got back from a 4 day vacation, and my water is now at 7.2. I have also noticed brown alge starting on my glass/sand/rock (which is normal from my understanding)

Started with live sand, but dry reef saver rock. Also started the cycle with Dr.Tims Nitrifying bacteria.

Should I just let me tank settle and bacteria battle it out before dosing back to 9 dkH? Or can I go ahead an dose it back to that over the next few days?

No corals in the tank, just two clownfish.

 

[Justfebreezeit]

You can do either. I personally wouldn't worry about alk till I add corals. I normally wait a month or so after adding my first fish.