If it was properly stocked and cared for it wouldn't look that disgusting. What gets me, is that he brags about working in a pet store for 2 years where he is the "fish specialist".
I once had a "fish specialist" at a pet store tell me that my fish got a bacterial infection because I changed the water more that once a month, and that 18 fish were too many. The tank in question: a 75gal mbuna tank, with all juveniles at the time. When I told her that I did weekly water changes, she just shook her head and said that was the cause of the bacterial infection, the water was too clean, and by changing the water I was draining out all of the beneficial bacteria. "Fish specialist" my arse.