I have an i180 cul deysnth, and it definitely gets tedious past i170. You start really running out of any fish that give anything at all, and by the time you get to 176 or so, only level 60 fish give anything, and only 0.01. Past that, the level 60-star fish are the only feasible option, and of those, Spring Urchin and Stupendemys are really the best choices. Still, the 60-star have a horrendously low desynth rate, and you will be seeing, at best, 50-65% chance even with full careful desynth buffs. 65% is the max success rate at 180 with full buffs. If Big Fish are two-star and they don't raise the cap, god help us all. XD