Yes, you are supposed to mix the water for at least 24-48 hours with a power head. There is a gas exchange that takes place while it dissolves. The water that you added, 45% of your tank volume, had no oxygen in it. That is certainly not good. The vitamins that you are looking for is Vitachem and Zoecon. Vitachem is rich in vitamin C and Zoecon is high in fatty acids and lipids. If they do not have those then you can substitute Kent Vitamin C, or other liquid vitamin C fish supplement, and Selcon. Rotate between the two on one meaty meal per day. For frozen foods, look for formula foods in a flat package. I don't know what your store will carry, it varies. There are formula foods that come in a cube also. These have a gel binder. Your fish may like it. I have bought it once and my fish won't touch it. You can also make your own food. Beth has a recipe in her Common Treatments FAQ. That may be better to do so that you can tailor it to suit the needs of your fish.