Ok,here is what's going on in my system compared to yours. First, i don't recall where you live but for me...it only hit 60 here so it's still chilly. That being said, most of the time my windows are still shut which means the CO2 in the house air builds up over time. So during this time of year my Ph runs lower, like 7.9-8.0. SO, isn't THAT a form of carbon dosing? Now, i run the air intake to my skimmer to outside air and that helps but i think you still get CO2 from your house air into your system. i don't feel that Ph level is to bad so why worry so much about ALK? Also, why concentrate so much on what one thing can do to a system,(like GFO).
I ran GFO,(Rowaphos), for awhile a long time ago and what i got out of it was...that it's dang expensive. I have not used any form of GFO since i read about LC. I don't even use LC that often. Now my NO3 is undetectable even on low range and that actually has me concerned because my corals do need some of it. I believe that if you use different methods in moderation they can all work together and even complement each other if some fashion.
Now only at the end of my 1st week of vodka dosing so i'm still waiting on the results but, in moderation, i'm dosing vodka as well as other things. First off, i decided though i still use GAC i only use it 1-2 day before a water change. Before the water change,(IF the PO4 level is above .03), i use LC. Then i blow out the LR and change to a fresh 200 micron sock.
I also, dose a kalk/vin mix , 1.5 gals @ night. I use 500ml of vin to 3 TBS of Kalk for a 5 gal mix and i make up 15 gals at a time. If there is any leftover vin then that goes as a carbon food source. Now for Biopellets. In the beginning i used them according to directions which was a HUGE mistake. I added a screen onto the bottom of a 2 little fishes phosban reactor and only added a TINY amount. less than an ounce. After 2 days i noticed all the corals both sps and lps react positively.
I think striving to maintain zero levels of No3 and PO4 is a mistake. What i'm trying to make a point of is that i think we get to fixated on one or two things and fail to see the big picture. Think of your system as a jigsaw puzzle.
To much of one piece and the rest won't be able to fit in.
So now, i think of the forms of carbon dosing that's going into my tank. CO2 built up from a partially closed area. Any excess vin from kalk dosing. A small amount from limited use of BP and NOW vodka. The only source that i really won't be able to control is the house CO2 that exits when i open the windows for the summer. Then my Ph will go up.
However, what i'm seeing ATM is a lower BUT stable ALK. Right around 7.7. I think the Bac population and the carbon input are balancing out. The Ph is staying between 7.94-8.0 for the most part.
As far as feeding. I think i feed moderately hvy. Even though i still have mainly sps and lps corals atm and just ONE fish. I feed a great variety of foods too. I realize there is PO4 that prob leaches out from the rocks. I'm not overly concerned about it. The LC i use cleans it up nicely and when i use a power head to blow out the LR i take my time. If you go slow you'll pass over a "honeyhole" of junk inside the LR and your filter sock takes it out.
So, as i look at it now, i see all these different aspects working together in moderation to help balance input and output. So far, my Alk and Ph are more stable and if i do see the Alk dipping low which it very slowly has been since using vodka, i hit it with 50 or 100 ML of Soda Ash solution and that tweeks it just right. I've only had to do that once since i started vodka dosing.
Now that my PO4 is better managed i noticed more growth, better calcification dispite the lower Ph. My Ca has been staying between 440-50. The skimmate is thicker. I do think that THIS is only part of the puzzle though. The others, placement and flow for example. I found that despite all these good things there are 3 frags that are proving to be a problem. Color and calcification are not the issues but PE is. Despite all the things i'm doing i do believe it was flow and placement because now i finally see some PE out of them. I guess the point i'm trying to make is not to place to much faith in any ONE method of carbon dosing and PO4 reduction because it might just be a combination of methods in moderation that work better together. Least for my system it seems to be working...so far