Did you focusing on the bubbling spots? The chance of encountering Feebas are much higher there. I caught one with this way.I caught a shiny Goldeen while searching for Feebas.
You know something is messed up when a regular fish is rarer than a shiny. @___@
Pretty sure I ran into a shiny Mimikyu during the ghost trial, because it looked more grey than usual.. except I didn't see the sparkles and I couldn't catch it anyways.. RIP Mimikyu.
Day six of SRing for that rowlet. it would be dumb to give up now so...