I just received my (somewhat expensive) Aqua Medic water test kit and I'm anxious to send in a water sample .. HOWEVER, over the holidays I went to Canada, and left my tank on "auto" mode, and this inlcuded four "14 day dissolving feeder blocks". I'm not sure what they are imbedded in, or if it makes any difference. I should have paid more attention. From Drs. FostersSmith ... Ingredients: Corn Gluten Meal, Wheat Middlings, Wheat Flour, Pea Protein, Brewers Dried Yeast, Lecithin, Dried Kelp, Dicalcium Phosphate, Canola Oil, Spirulina Algae, DL-Methionine, Garlic, L-Lysine, Vitamin A Acetate, L-Ascrorbyl-2-polyphosphate (source of Vitamin C), Vitamin D3 Supplement, Vitamin E Supplement, Thiamine Mononitrate, Riboflavin Supplement, Niacin, Folic Acid, D-Biotin, Copper Sulfate, Zinc Sulfate, Inositol, Mineral Oil, preserved with Methylparaben, Propylparaben, BHT, and BHA. Guaranteed Analysis Crude Protein 1.50% min Crude Fat* 0.060% min Crude Fiber 3.00% max Moisture 18.00% max Calcium 19.00% min Calcium 21.00% max I didn't notice the "Copper Sulfate" before! I'm guessing "Dicalcium Phosphate" is some part of the white block thing. Maybe it's the wheat flour too. Anyway, I'm wondering how much of an effect this will have on the water analysis. But I didn't want to do a full water change either because then it is not indicative of the contents of the tank water TYPICALLY. However, to get a good analyis, I'm thinking maybe I'll be forced into a large water change and wait three weeks? Or do you think the food pyramids is a negligible factor? In any case I'll probably not use them anymore and rely only on my two auto-feeders, since they seem to be able to last several weeks. What do you think?