DHeckel--- I broke down your post and tried to cover all your questions-----
I have started to dose white vinegar as per the instructions in this article. I am currently dosing 4 ml per day.
I also have a chaeto bed and run GFO (Rowa) and carbon (Seachem Matrix) in two separate reactors. Although I hardly ever get any nitrate (Salifert) and phosphate (Rowa Merck) readings, my front and side glasses get covered with green film algae every two days. I do not have any hair algae on glass or rocks. I am assuming that the total phosphates must be high as I use the frequency of glass cleaning as my biomark for the presence of bad nutrients.
Don't assume they're "bad" nutrients........film algae is fine and the corals are taking up some of those nutrients too. I don't think I'd bother to reduce levels anymore if your colors a deep and vivid.
So, I have decided to introduce some carbon source to the water column to increase the amount of bacteria to reduce bad nutrients further. I am intending to decommission my phosphate reactor in a few weeks time. However, I will keep my chaeto bed as it stabilises pH as well as provides safe heaven for zooplankton.
I only use GFO to knock down high PO4 levels otherwise, I'd just take if off now if you're going to dose vinegar. The GFO is taking away PO4 the bacteria needs to grow. The Chaeto will compete for nutrients too, so I'd eliminate that too.
If you're going to run a bacterial based system you don't need those other export crutches. The idea is to simplify things.........you want to control things with your dosing levels......with other variables like GFO and chaeto it limits your control.
I would like to know how you decided that 15 ml of vinegar per day is enough for your tank.
When I was dosing too much I'd see white sludge in my circulation pumps or other areas..........you don't want any of that. Your PO4 can also keep rising if you get to zero nitrates and you keep raising your dose levels. That's a sign to cut way down. As long as I'm under .10 phosphates I'm good, I don't chase each tenth of a point.
I will use the following two criteria to decide to stop fix the amount of vinegar to be dosed in my tank:
1. the frequency of glass cleaning drops once every four to five days or more
2. chaeto growth continues at a steady pace (perhaps not as vigorous as before but does not slow down )
What is your opinion on my methodology?
Pay attention to coral growth and colors. If you have a balanced system you can see new growth almost every day. When the lights come on you should see the bases killing coraline or new tips sprouting, ect.
If your levels are already good and your corals look good, I'm not sure I would dose vinegar at all. If you want to eliminate GFO, chaeto and make things more manageable and controllable than dosing is fine. Just be patient, you may have to go through some minor ups and downs. Make sure you have plenty of snails, your coraline is growing good, and keep your rocks basted.
A lot of people give up and blame the vinegar to not working when in fact they don't have a good skimmer or aren't getting the nutrient laden bacteria to the skimmer. Any kind of filter bags will catch bacteria and if you don't change that daily they just die and release the nutrients back into the tank.
I opt not to use any filter pads or bags. Make sure you have good flow in the tank and minimal dead areas.
When everything is working good you shouldn't be able to see any detritus out of the rocks when you baste them.