list of scaleless fish?

Hi all,

I have been wondering which loach species are considered scaleless.. I
assume not all are scaleless?

Is there a list somewhere listing all the species that are in the
scaleless family, and thus have to worry about medication strength?

I currently have dwarf chain loach (b. sidthemunki) and zebra loach (b.
striata).. not sure if they are considered scaless.. I don't think they
are, but I'm not very knowledgeable about this.

linda