it is pretty common that some fish are going to die when a tank is being stocked. sometimes it is because the fish already had a problem from the shop or shipping, or perhaps it is because its new home isn't properly maintained. Many people that are setting up new tanks get in a hurry and add too many fish too quickly. It is important to add fish slowly, 1 or 2 at a time and several days apart at least. As for clown loaches, it can be hit or miss. The older, larger loaches tend to thrive very well, but juveniles, like the ones usually sold at pet shops, are delicate and require nearly perfect aquarium settings. I stay away from these loaches and instead opt for yoyo loaches, which are smaller but beautiful and hardy, as well as fun to watch. Try some yoyos, adding 2 at a time until you have 6 or so.