The Black Ocean in Kpop is when a large number of fans agrees to simultaneously turn off their lightsticks during a designated group or singer’s performance as a way of showing their dissatisfaction with such group/singer due to some issue. Though generally done by fans to groups or singers outside of their own fandom, there have been cases when fans turn against their own members or group in reflection of turmoil within the fandom at the time.
How to react?
It might be hard for some to contain their anger and smoothly take on the situation. These things can suddenly happen and people might urge to fight back. But the best thing is to tell the person kindly to stop what they are promoting and delete any comments about the black ocean. We can't stop the community all at once, but one by one we'll stop the word from spreading.
2008 Girls Generation
The first Black Ocean was, probably, during the 2008 Dream Concert Girls Generation Performance with the formation of the CARTEL and the participation of the rest of the attending fans. Black Oceans are a really hard thing to achieve. SNSD might have encountered this because their own fans have turned on them while they had a very small amount of fans. In 2008 SNSD was near their debut before they actually grew in fame with Gee.
BTS has already received a Black Ocean before in 2015 MAMA Awards. Another major controversy between all of the fandoms. Some say it was not intentional, some say it was planned on purpose. 2015 MAMA Awards, BTS performed I Need You and Dope. Here, a fan at the concert had posted a live tweet reporting the ARMYs there seemed to be a black ocean. This had fired up a lot of fans, Exo-Ls and ARMYs all had different approaches. This was the point when EXO-Ls and ARMYs where getting into tension of popularity.
Sadly, it's part of fame. Seventeen, Lovelyz, SNSD have all experienced this tragedy.
And it might be depressing and no idol group should experience this, but this is just another obstacle made for them by haters. And haters? They will encounter them more and more as they gain fame.
Who was behind the BTS Black Ocean?
EXO-Ls are the main people behind this after the Lay and ARMY rumors floated around the internet. But it's not all EXO-Ls and all about the rumor. The EXO-L who started this tweeted it was her mistake as she was angered by fake ARMYs who happened to be EXO-Ls who decided to disguise as an ARMY. Of course there's that rumor, but jealousy and tension is probably the biggest reason for this.
2016, BTS gained a lot more attention and fame over Fire and WINGS. EXO-Ls are now actually worried that BTS might break EXO's record of 4 Daesangs in a row.
EXO-Ls aren't the only one. Other fandoms including igot7s and inspirits, (got7 and infinite) etc., etc. are taking a part of this event for the same reason of jealousy and the worry of another group and fandom they have to break through in order to get to the top.