The Spaniard made seven birdies and an eagle at Chervò Golf Club and while two dropped shots on par fives took some of the gloss off his round, he was in the chasing pack behind leader Laurie Canter, who carded a stunning 60.
Arnaus secured three top tens in his rookie Race to Dubai campaign last season and finished in the top three at the Omega Dubai Desert Classic in January.
More good signs could be seen in the recent Rolex Series events, and Arnaus insists he will be not be holding back as he goes in search of a maiden European Tour win.
"I’m really happy with how I played today," he said. "It’s a good start and honestly I felt very comfortable out there.
I’ll keep in the same mindset, going for it, and hopefully the next few days will be better
"I had a lot of chances, a couple slipped away and I dropped a couple of shots on the par fives but I’m really pleased with where my game is at and I’m really looking forward to the next few days.
"I’m just trying to attack and sometimes it turns out well and sometimes it doesn’t. I’ll keep in the same mindset, going for it, and hopefully the next few days will be better.
"I came around here and saw that there’s not much trouble around. I just wanted to hit it as far as I could and take some bunkers out of play and cut some corners. That’s what I’m doing it and I’m enjoying it.
"The confidence is right there, pretty high I would say."
Joachim B. Hansen went one better than Arnaus with an opening 64 and he believes the par fives will be crucuial if he is to continue his good form after a top ten at the BMW PGA Championship.
"Just the round I was looking for," he said. "A bit lower than I expected but you’ll always take eight under.
"My putting was really good - holed a lot of putts. My irons were really good as well. The only thing I consider that went wrong was the driver - I could have hit a bit more fairways.
"The short par five on the sixth hole and the other par fives are reachable. There’s a lot of opportunities.
"I worked on ball striking, hitting the ball more in the middle. When I hit it in the middle of the club, I produce good shots. I just need to do that more."