Blue Ocean, a U.S. alternative trading system (ATS), has suspended overnight quote dissemination for four securities heavily traded by South Korean investors through leveraged ETFs (funds designed to magnify market returns). Trading remains available, but the loss of live bid-ask prices means investors must submit orders without seeing current prices. Effective from the 1st, the halt covers SOXL, a 3x leveraged Philadelphia Semiconductor Index product; KORU, a 3x leveraged South Korea index product; SNDU, a 2x leveraged SanDisk product; and RAM, a 2x leveraged DRAM ETF. Blue Ocean said the change was required under U.S. Securities and Exchange Commission (SEC) rules, which prevent a single ATS from executing more than 5% of a security's average daily trading volume in four of the preceding six months. Concentrated Korean retail trading, particularly in SOXL, appears to have pushed Blue Ocean above that limit. South Korean brokerages plan to keep offering limit-order trading through other ATS venues, although those venues also do not provide overnight quotes or real-time prices, effectively creating blind orders. Brokerages have offered Blue Ocean overnight trading from 10 a.m. to 6 p.m. Korea time, or 9 a.m. to 5 p.m. during daylight saving time. South Korea represents about 35% of Blue Ocean's overnight volume, while Korean investors' U.S. stock trading increased 34% from $48.9 billion in January to $65.6 billion in June, according to the Korea Securities Depository. The development is likely to weaken Korean retail investors' leveraged investing. After the earlier Samjeon-nicks leverage incident, individual leveraged securities, including those listed in the U.S., became subject to a 30 million won base-deposit requirement; index-based leveraged products had been exempt, but their loss of overnight quote visibility is expected to constrain daytime leveraged investing as well.