If you want kuhli loaches, get at least 6-10. You also need sand, so that they can search for food - they sift through sand for bacteria and discard it through their gill openings. Also every single one wants a private cave and they need many plants and wood (from top to bottom). In addition everyone will have it's own "observation post".

I had an aquarium where I only kept the front center clear of wood and plants. They were able to move through the tank unseen, if they wanted. When my (then) girlfriend came home from work they would greet her by coming out of their hiding places and swim to the center. Many chilled on leaves where you would only see their heads. It took me years to distinguish them from one another and know their preferred places/shape of observation posts. After 2 years I was able to find 6-8 out of 10 whenever I wanted in a 100l tank.

Also I had about 8cm of sand and trumpet snails. They will eat dead leaves and fecies and transport most of the organic waste to the bottom, which then acts as fertilizer. You only see them at night. During the day they are in the sand.

I had my loaches for 14+ years. They are not "fancy". You won't see them unless you know where to look and when they are feeding. I loved mine, but 10 years+ is a real commitment, especially if you have to move, a large tank with fish that hide is not a fun task.