In my super-duper awesome file (as opposed to the first-time file and the nostalgic play-again files), I’ve captured every monster but one in the Omega Ruins. I know it’s called a Halma, and I’m assuming it’s a shelled creature since that’s the only species creation I haven’t unlocked. I’ve never even run into one that I can recall. Is there some place where they may spawn more than others in the ruins?
I believe I remember fighting them more often right at the entrance to the ruins. It’s been a while, but I remember having problems finding them as well.
hmmm I finished the whole monster arena thing. But for the Halmas, I don’t think they spawn in a certain area of the omega ruins. For me there all over the place when I enter the ruin. Try going through the ruin once, and if you don’t find one keep looking because eventually one will pop up. I have faith in you so now go and TRY IT!
If it’s the giant turtle, Kagon got it right: They spawn near the entrance.
The giant turtle is the Adamantoise - I’ve run into it more than a few times already, no worries there.
I’ve also had a lot of trouble finding Spirits and Black Elementals, but the Halma’s just too much. I’ve never not even run into something before!
I mainly just ran around where the save point was and eventually got them all.
Right, I just loaded my FFX copy and checked it out. Still the same deal though, stick to that area.
I finally ran into two Halmas with a Spirit in that first area - I guess perseverance pays. Thanks for the encouragement! 
(Now I just need 8 more, ha.)
hay guys wheres pikachu? viridian forest?
You aren’t funny. Troll elsewhere and consider this a warning.
Agh, this topic makes me want to replay FFX just to capture all those monsters. That was like the most fun minigame-kinda-thing for me.
Lav :3