One difficulty I do have is recognizing what ingredients my fish need and what is just cheap filler. Going through the samples that I got from Supercichlid.com, I finally found one that they like. It is NLS Probiotix, which seems like a gimmick, because how could you even maintain a probiotic culture in a pellet food? But the rest of the ingredients look good, and all of my fish eat it.
Probiotics have been used in fish food for quite a few years, and there are many scientific studies that show the benefits of use (as well as possible negative points of over-use). Insofar as manufacturing of pellets and maintaining the cultures: "....heat-inactivated versions have been shown to retain benefits for the host." (http://www.global-engage.com/life-science/prebiotics-probiotics-synbiotics-aquaculture/), so if done properly it's not much of an issue I'd guess.
When I feed fish foods with probiotics to my large Flowerhorn in bare bottom tank I can easily see he has less waste compared to foods that don't contain them. That said I try to feed a balance of both types.





