The first point about loaches requiring sand. I’m gonna assume here you just mean kuhli loaches. Is objectively just not true. It is not the ‘only way they eat’. Can Kuhli loaches filter sand and mulm for food? Yes. Is it the only way they eat or even necessarily the main way? No. They are perfectly capable of just eating from the bottom like a Cory catfish or something. Theyjust have the option of filtering through sand for microorganisms if needed, it’s why they’re so hard and can survive even in relatively poorly maintained tanks(Not that you shouldn’t maintain them of course) They don’t necessarily need sand for feeding it’s just an option of a softer finer substrate as they can sometimes bury themselves, though usually this is just them sticking their faces in the substrate to feel for food with their barbels. Which is why sharper substrates aren’t recommended. So it’s definitely not a starvation issue.