Turtle Mommy,
Just for a suggestion to ponder, you can purchase sewer and drain PVC pipe which is a sort of lime green in color (all the way through). Not sure how small of a diameter that pipe comes in, but I know that 4" to up to 16" is quite common.
I just purchased 120 feet (12- 10 foot sticks) of 6 inch diameter PVC pipe and it cost me about $380-$400.
If you were to use solvent to remove the printing and rough the outside of the pipe up with coarse sandpaper or even a sandblaster, it might look really swell in a pondscape layout. No painting, no staining, it would hold its original lime green color for a long, long time! Algae might even grow upon it and really camoflauge it nicely.
You could ask a local plumbing shop (ask several of them) and a few contractors to save all of their scrap pieces. They cannot usually use the short lengths of leftover pipe and that typically goes into the trash. You might end up with various diameters, which would make for an interesting variance in looks.
catfishnut