Very doable as a level 61 Beastmaster/Ninja. My gear is as follows;
Light Staff.
Beast Jackcoat
Beast Helm
Beast Gaiters
Beast Trousers
Beast Gloves
Amemet Mantle
Bird Whistle
Corsette +1
Pearl Ring x2
Melody Earring x2
Use Utsusemi: Ichi and whatever food you plan on using (I use Tavnazian Taco). If you're lucky you can bug a White Mage for a Protect IV (It will help in case things to awry). Charm the closest monster and have it fight Aquarius. Run into the hall between the room that Aquarius spawns in, and the room where Ellyllon spawns. Face towards Aquarius while targeting one of the two spiders in the room. As soon as your pet dies charm the spider and send it to its death. Run into the room with the five Death Caps and do the same thing. Next will be a hall with three spiders and a left turn. Charm a spider, send it to his death. If you keep going straight, there will be a branch to your right that will lead you back up to the entrance in case of failure (Hug the right wall at that point). Hopefully you will not have had to use that turn. Moving on... Further ahead of you will be a small room that has a couple spiders and a couple Death Cap.Charm one, send it to die. This room has a branch to the left that will lead you back to where Aquarius spawns. From here on out it's just a matter of repeating what you were doing and keeping shadows up. Always have three. Always. If he hits you and removes one or two shadows before your pet can attack him, run to your next charmable pet and start casting Utsusemi. This WILL take you quit some time. He has 6600 or so hit points, and will periodically use [METALLIC BODY] (Ie; Stoneskin). He will be hitting you for between 200-300 damage. Your pets average lifespan is around 20 seconds. I recommend learning the map and all spawn points of the monsters first. Don't use [SIC] as no pet will ever have enough TP to use a TP move unless you managed to [CHARM] and [FAMILIAR] something. Knight Crawlers make great tanks, but are harder to charm and should be close to Very Tough for you. Warp Cudgels are your friend. Don't be afraid to zone him if you have to. I've noticed that if you zone him or if he kills you, often times he won't un-spawn but will rather walk back to his spawn point.