Thanks for the advice. It's from a local orchid show years ago and says only "MSU formula" plus the dosage. I guess you are right that it's a repackage. Sources online shows the MSU formula (for RO water) should contain (13-3-15): Nitrate Nitrogen 12.5% Ammoniacal Nitrogen 0.5% Phosphorus as P2O5 3.0% Potassium as K2O 15.0% Calcium 8.0% Magnesium 2.0% Iron 0.17% Manganese 0.08% Zinc 0.04% Copper 0.04% Boron 0.01% Molybdenum 0.01% From my limited knowledge, those ingredients look fine to me. I just want to make sure it doesn't contain some heavy metal or strange hormone. Although I have no idea whether their concentration matters or not. On researching this question, I found that actually it's not easy to say whether a product is approved-for-use on food crops, as Dave said. Other than those that are specifically designed for vegetables, many generic fertilizers don't mention whether they can be used on food crops or not. Like the DynaGro Foliage Pro I have been using, I couldn't find a reliable source that states that product is safe for food crops.

MSU has both types of fertilizer - normal tap water formula and for rain/RO water. I use MSU but Dyna Grow also makes a good product and both should give you good results if the rest of your culture is correct. Brooke

Go with Mr. Ray. His price on MSU formula is unbeatable. --Stitz--

I find that deciding how to fertilize is up to each grower's environment, water quality, and judgement. So it is not always a simple conversation. Everyone has a different opinion. However, most will tell you to ignore the label and fertilize more frequently at a weaker dosage than the labels imply. Here is what I do: I fertilize with every watering using .25-.5 teaspoons per gallon. I generally use the MSU formula fertilizer or Dyna-gro Gro or Bloom. I switch to the bloom late summer to late fall, but I have not noticed a difference. Once I use all of the Dyna-gro Bloom I will just go back to the MSU full time. I add CalMag and a mirco-nutrient pack once a month. I think I have a solid fertilization regime, but it is not stellar. Most importantly it works for me and 90% of my collection. And it has worked well for my Phals in the past. I like the way First Rays explains fertilizing: Explaining fertilizer dosage You may want to look at some of his other articles also.