
Hi, jamarm.
WELCOME TO FISHLORE!
YoYo loaches would be a fine addition to a 55 gallon tank, they like company, but it should be of their same kind. You will enjoy very active fish that feel at home if you have 3 -6 yoyo's together.
Clown loaches can not be housed in a 55 gallon tank. 75 is a minimum size tank to start with as these fish rapidly grow to 5 to 16 inches, need lots of room for their fast swimming and bulky body type. I found a link that will explain.
http://www.loaches.com/species-index...a-macracanthus
Hope this helps. What else is going to be in your tank? Loaches do best with a sandy substrate..and very clean water conditions, as they are susceptible to ick and are scaleless which makes it hard to medicate them.