Yep, happens in my bottles after opening and time. Pretty much use ReaSea AB+ only now.
unfortunately, no product is completely safe, AB+ included!
Several people have reported finding bits of black plastic in their bottles of AB+ too. There have been a couple threads here on R2R of it happening with pictures. It appeared to be bits of black plastic mixed in. I think someone had pictures of a destroyed bottle cap in the bottom of their bottle too, so I'm guessing the machinery that bottles the AB+ eats a bottle cap off a bottle from time to time and bits of black plastic shavings get mixed in with the product occasionally. Maybe they've cleaned up their QC measures, so maybe it doesn't happen any more.
I still use both products daily, I just take an extra peak into a new bottle now looking for anything strange. haha.
I dose Acropower, AB+, Aquavitro Fuel, and ME Polyp Extender every day.
No definitely not from the cap....usually starts showing up within a couple of weeks of opening. This is a direct response from TwoLittleFishies.....
"That is a precipitate that happens sometimes because we make AcroPower at nearly the saturation point for some ingredients. So, to answer your questions, no it is not normal, but it is not rare either. It is not harmful. Yes you can decant or filter out the white precipitate and use the clear solution. The strength is reduced from a fresh bottle, but it will still work."
I seem to get it in pretty much every bottle now....maybe it has something to do with being exposed to air every time the cap is opened (since yours is dumped in a dosing container and left alone)? Strange either way.
I'm not sure if that is it either since my dosing containers are exposed to air. In order to keep them from collapsing when the dosing pump sucks product out... I have a small vent hole drilled into the cap of each dosing container to let air in. They are not sealed. In fact, my acropower would be exposed to air more often than a bottle that is only opened once day. Mine sits in a vented container for 2 months... and no precipitate.
And it seems if it was an over-saturation problem leading to the precipitate, then just warming the bottle a little, or adding a bit or RODI (diluting it) would clear it up again.
I have no idea... if I had to have every answer in this hobby, I would have quit it long ago!