Little white lines at the bottom of my sky textures

This is something that has plagued Tortured Planet for a long time. How do I get rid of the ugly white lines at the bottom of my sky textures? At first, I thought it was because they had exceeded the 255-pixel limit, but that can't be the cause because (a) only one of the problematic sky textures exceeded the limit, and (b) when I corrected that, it didn't change a thing. So what's the actual cause, and what do I need to do to fix it?

This problem is also seen in many official SRB2 skies. I think the way to fix it is to make the sky texture 256 x 256 and use two patches. You could use the same patch twice if that doesn't look to strange.

I think skies might have a strict limit on what size they can be. Try either making it 128 pixels tall, or make it 256 but split it into two patches.

I had the same problem too in SRB2Heroes. It only got solved by splitting them into multiple patches. You said you tried that, Fawfulfan, but try again with an even lower resolution for each sprite. And you don't need to tell me that doing that is a bit of a pain.