I have never had problems with freeze dried foods. I use them on a regular basis. I rotate flake, pellet, frozen, and freeze dried. I think the key is variety. Last night I even fed my fish some fancy lettuce. The silver dollars were like little pirhanas(sp). The label of the freeze dried plankton I use reads "feed two to three times a week in conjuction with other staple foods." I agree that live/frozen is the best way to go, but I'd like to know the logic behind people thinking freeze dried is not good for fish.
Durbkat, Dr Foster and Smith sell daphnia. It's a little pricey, but it's supposed to clean out the fish. I have not used it, but it may be helpful for your fish. Another product I'm prety happy with is Marineland Labs "Bio-Blend". According to the analysis it's pretty healthy. For frozen food, I like the SanFranciscoBay brand. I use the freshwater multi pack. Once again, variety. Good luck.