These two very different people please each other. Capricorn's strong, dominant personality is just what Pisces needs. Pisces feels secure with practical, determined Capricorn who can take charge and make decisions. In turn, Pisces brings a breath of romance and idealism to Capricorn's staid approach to life, and Pisces's lavishness with praise and affection delights Capricorn. Capricorn does not easily verbalize its deep feelings, but Pisces intuitively recognizes Capricorn's loyalty and passion.
Sex is fine, and their contrasting temperaments neatly complement each other.
Sexually, this might be fun since they are both venturesome in entirely different ways. But Aquarius is detached, interested in ideas and the world at large, while Pisces is interested in sensual fulfillment. Eventually, outgoing, social-minded Aquarius will start looking around, and Pisces can't endure that. Independent Aquarius needs freedom and after awhile resents Pisces's struggle to keep Aquarius caged at home. If all life's problems could be resolved in the bedroom they'd be happy, but both need what the other does not have.