My theory on locations (a modification of T2 theory) is this: compute b = (X-Y) mod 866 (where (X,Y) is your coordinates).
Fish bands have b between 0 and 210. Carp/serpent are close to 0 end, Chromis Phagrus towards the 210 end. This checks with all the locations posted on the wiki so far (except three, where the results are 857, 223 and 233, which is within the oscillation range from T2)
Just to recall, the formula in T2 was (X+Y+80) mod 866 and the bands oscillated 20-30 coordinates.
Phagrus
1308,3707 b=199