Not sure what what I said about Slay em all is wrong to you. Youtube is really close to killing my interest in watching aquarium vids. Even if you ignore the torture thumbs,they still post them.
Mullen hasn't shown any advanced fishkeeping skills that i've seen. He once boasted he sold $20,000 of Discus in a month. Last I saw,he doesn't have a single Discus tank. He's never shown any breeding skills period. He buys his fish,and few if any of his are hard to keep and need skills.
He's not the last word or any word on any fish that you NEED skills to keep.
No Jellyfish tanks..
He's sort of painted himself into a corner..keep adding tanks and making money from youtube. Sort of like a pyramid scheme.
I predict,one day he will do the talking..and we will later learn his employee's will be doing all the maintenance. I don't think he's really that much into fish much..he just found an opportunity to make big bucks and smile a lot.