I want to get a group of kuhli loaches anything I need to know
Get them from a good supplier as they can sometimes be sick, get as large a group as you can to keep them happy, and give them lots of hiding places and tubes to make them comfortable.
They can be shy fish so keep them in a large group and give them loads of cover. Give them sand because they like to bury themselves in it and they like to sift through the sand. Feed them small sinking foods and frozen foods. They prefer soft acidic water but will adapt to most water.
how would I clean the sand
Since food, poop, etc doesn't fall through the cracks like it does in gravel, it just sits on the top of sand - usually easy to see. I just "hover" my aquarium vac tube over it and it sucks it right up.
You just use a siphon and hold it a little above the surface of the sand. It's actually easier to keep clean than gravel IME because dirt falls between the gaps in gravel but it sits on top of the sand.
Would the sand potentially scratch the eyes of my other fish
No, most fish are from places with sand naturally so that's not a problem
Would the sand be bad for golden zebra loaches and or plecos. Could they swallow it and if so would it be harmful?
No, pretty much every bottom dwelling fish prefers sand to gravel. If they swallow it it is much more easily digested and pooped out than gravel and causes no problems
Would the pleco still like some rocks to clean off
Loach and pleco
Separate names with a comma.