 Intended as a replacement for the VAX 8800 family, the two models differed in their performance level and coolings system.The Aquarius was a high-end machine using liquid cooling ( is the water-carrier) seen on IBM systems, while the midrange ("dry") was air-cooled.The first Aridus models delivered were "field-upgradeable" to "Aquarius", but Digital officials thought nobody would require it, so they didn't offer it.