Aspen aims to offer digital asset management to institutional and sophisticated investors.
Terms have not been disclosed although the investment was disclosed to investors during a webinar in March.
The asset manager disclosed Thursday its shares in the Ethereum trust were worth $4.75 million as of March 31.
The manager of $1.4 billion first bought bitcoin trust shares in 2017.
Financial advisory firm Rothschild & Co. issued an unusual warning on Monday: stay away from a fake and fraudulent digital currency.