In the eyes of Islam, it is haraam to increase your wealth without any effort. As I can say for example you put some money to a man and from that money If you are given more money then it is completely haram. I mean, as you put some money at interest, the money that you get in addition to your honor is completely haram. In that proportion Since you will be stacking then I would say that it is haram in the eyes of Islam if your capital is increasing through stacking.
Yes, this is already explain everything. In my country, atleast, Bitcoin itself is haraam (well, some say haraam and some say it's not). There are some articles that says :
"Bitcoin is
Mubah (legally permissible) as a medium of exchange for those who are willing to use it and acknowledge it. However, Bitcoin as a legal investment is haram because it is only a means of speculation, not for investment, only a tool for playing profit and loss, opening a profitable business."
So, if you use Bitcoin just for a medium for exchange, that's okay.