http://www.great-blue.jp/?aid=066&lng=en
There are only two ponds. The E-8 one is the pool for zebra eels, and is surrounded by scorpions; you can't catch Ryugu Titan there. The F-11 pond is the one Aihree is talking about, and is the only place in Den of Rancor you can catch Ryugu Titan. I've never tried it myself, but there you go.
Not sure about bait. You could probably figure something out looking at the list of fish that bite there.
VVV Looks like sliced cod and meatballs catch the same thing in that pond. Sliced cod could still have a higher bite rate from titans, though.
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