this is true, natural is good/better. my UV is active because of ich. but IMO to help quickly reach the best water qualities this can be very useful. u can get by without those bacterias, the problem is when the equipment fails ur screwed cause the tank will not be able to handle the change. its like allergies, i.e. the lack of exposure to a foreign agent, or what ever. so its a double edged sword....i guess it all depends on whether ur willing to let ur tank sort things out or are u going to intervene to create the perfect environment that couldn't cope with mechanical failures and outside variables. its like the difference between a sheltered child and one that was allowed to do their thing.