I've created a Large world for farming purposes. What I've discovered is that the Fisher NPC gave me a quest to fish a couple of fish out of Sky Lakes. I'm aware that these are typically naturally-generated as floating islands, but I'm wondering if these must also be in the Space biome to be considered actual Sky Lakes. The natural floating lakes in this world all spawned in the Surface biome (height), and it seems like I cannot fish any Sky Lake specific fish out of them.
Note the biome information at the top-right.
Am I just getting terribly unlucky, or did this spawn too low to count? Can I move it up (with pumps), and if so, how high must it be?