well i wish him luck, best to get on those water changes, that really means the world for growth.
Maybe a month.my rss slowed growth drasctically around 4", I still dont know why. But a year later both my sevs are pushing 6.5" I do twice weekly 30% changes. How long has he been that size? I've never heard of sevs growing this slowly but both of mine have.
Water changes don't stress fish.All fish grow at different rates, sometimes vastly different even same species in same conditions. Same as any other animal.
Only thing that could be an issue is if the huge daily water changes are stressing the fish purely from the disruption to the tank.
Water changes don't stress fish.
I don't gravel vac every day, just the wc's.I don't know what your procedure is like, but if there's a lot of disruption to the tank then they most certainly can stress fish. Bit like if you try to gravel vac every day, not all fish are going to appreciate that.