alk and a couple other questions

[a.browning]

Hey everyone, I've had my 55 gallon tank up for a while, everything has been growing great. I have it filled with assorted soft and lps corals, which have all been doing excellent. Recently, my polyp extension hasn't been as good and things just dont look so happy. Even my corraline is starting to fade to white. I've been tracking alk for the past few weeks and its gone from 8 to 7, and after this week's water change it maxed out between 6 and 7dkh (API test kit). I do weekly water changes with IO reef crystals, 10%.

I'm thinking the corals aren't happy with the low alk. I've read about dosing baking soda, and baking it first in order to raise ph. My pH is usually only about 7.8 so I figured baking it would help out. I just wanted to check with you all and see if this sounds like a good idea and maybe see what others thought about dosing baking soda.

My second question is about top off water. I have a top off tank, should i use a bubbler or pump to keep the water circulated in there? I don't want it to get stagnant. Thanks!

55 Gallon drilled
Reef octopus skimmer
BRS Carbon reactor
15 gal refugium
mag 5
koralia 750

ammonia: 0
nitrite: 0
nitrate: 0
alk: between 6 and 7 (right after water change)
cal: 430
p04: <.25
pH: 7.8-7.9

[sedor]

If your corals are pulling more Alk out of the system than your water changes are accommodating for then its time to start dosing. Keep in mind though, Alk and Ca and Mg all balance each other out and need to be dosed together. For instance, you should be dosing equal parts of Ca and Alk daily and then Mg every week or two when it starts to get too low.