Trouble Getting Alk up in established tank dosing Nitrates

[gregzz4]

Right now, are you dosing 125ml Sodium Carbonate, or Sodium Bicarbonate?
Remember you need to use twice as much SB as the recommended dose of SC if you are mixing per Randy's formula.
Personally I've never dosed SB so double-check the methodology as I can't advise you there.

You mentioned at the start of your thread that you dosed then tested the next day with no change. Keep in mind that your tank may very well be using as much or more than that dose daily. I've had my total system volume of 115g use easily over 100ml daily, and you have a lot of big consumers.

If it were me, I'd check the Alk right before dosing, and then @ 30 mins and 1 hour after.
This will let you know whether the mix and the amount dosed are correct.
If you don't get the desired effect there are a couple things you can do.

One would be to test your mix. Randy states 1ml of his mix raises 1g of water by 1.4dKH.
Add 5ml of your SC mix to 1 gallon of RO (presumably 10ml SB?). This should give you a result of 7 dKH. Then add one more ml (2ml SB). This should take it up to 8.4dKH.
If you're not sufficiently close to those results, revisit your mixing instructions/methods.

Next thing would be to have your LFS test your Alk, Ca and Mag to rule out kit and testing errors. Remember that low Mag will prohibit raising Alk.

After you know for sure that you're good to go, you can then confidently start with testing 24 hours later to find your daily dKH usage.
Once you've done that for a couple days you can go ahead with the additional dose to start raising it.
Personally, and because you said you're good to go slow, I wouldn't raise it by more than 0.5dKH daily, although some state it's safe to go as much as 1.0dKH daily. I see no need to rush it.

If it were me;
Once I found the daily maintenance dose I'd use a doser and spread it out over a 24 hour period. I had mine dosing every 2 hours.
For the additional dosing you can do it manually or add it to your doser timing, but still spread it out over the whole day.