Reef Builders is top notch for educational purposes. Same with Melevsreef. I also enjoy watching more "slice of life" stuff like Inappropriate Reefer as he typically just shows off his tanks and talks about what he thinks is working for his setups and whatnot. I personally appreciate his personal and casual approach to the hobby and I find it more relatable than other channels. Coralfish12g for entertainment as he usually does more than just educate and his videos are fun to watch.