I'm dealing with anaerobic bacteria in my microbiology lab now. I dont think it can grow in the sand bad. There has to be absolutly no oxygen in a medium inorder for it to grow. That being said, I'm sure the bag of sand still has traces of O2 which means theres alreay die off in the bag of sand, and with the hash conditions of the enviroment its in (not the largest amount of nutrients since its in a closed enviroment(nothing comming in or out, except for the initial packaging)) I doubt theres enough of them to cause a detectable ammonia spike due to the fact that they cant reach colony levels. If there was that many of them in the bag youd see them(they look like a milky colour and jello-like in colonies).
I'm going based on what I did in my lab using anaerobic bacteria, so I might be wrong. The media we used was Thioglycollate broth, which has reducing agents(eliminate O2), agar (limits diffusion), resazurin (a dye that acts as an O2 indicator). The bacteria would only accumilate and multiply near the bottom of the test tube, since there was zero oxygen there. It also had perfect conditions to multiply which I doubt it would have in a bag of sand (incubated at 37C, tons of nutrients, and absolutly no O2). But then again theres other types of bacteria that only require little amounts of O2 to grow(only 5-10%
, but I think those would have a hard time also once the O2 is gone i nthe bag.
When I first set up my tank I cycled it with uncured live rock and live sand, but I added it straight to the tank (together). So I cant really say if the sand gave me an ammonia spike alone.
Therefore, I'm not sure about this, but from what I know I doubt theres enought anaerobic bacteria in the bag of live sand to cause a noticable ammonia spike.
ONE AGAIN I'M NOT SURE, you might want to research more before doing anything, but if you said that you added the new sand into your tanks before and its the same brand, that gives you a little more hope for it.
But like Henry said, why use live sand to cure the LR?? Just get a piece of cured LR from your tanks and throw it in the bucket to seed it.