Clips to hold seed pixels to 1/2" PVC. PETG works well. They are mainly used to keep the wire from flopping around in the wind. I would still use zip ties at the ends or wherever you need to take weight off the clips.

Clip_Seed has a 5mm slot for the seed's wire.

Clip_Wire has a 7mm slot for larger wire. It can work for seeds also.  The 18 gauge 3 core flat wire I used was a bit larger than the seed's wire.