Old thread, but common problem it sounds like. I agree w/Shazaam that the small amount of cross contamination you've created wouldn't cause significant precip. I realize that this thread started a while ago and that the original poster may no longer be following but I figured I'd give a little insight from a chemistry perspective. Long term storage and temperature fluctuations will cause different components to solidify by a variety of reactions. Diluting the stock or re-dissolving the precipitates after decanting can deal with some of this. I would warn against heating the entire stock as this can cause problems. If the FP has formed solids after experiencing a period of low temp, that is likely just salts that have formed due to their lower solubility at lower temps. For the precipitates that form, I'd guess they are either Calcium Phosphate or Calcium Sulfate. As redshirtcat mentioned, there doesn't seem to be much sulfate in FP so I'd guess phosphate is the culprit. In either case, both calcium sulfate and calcium phosphate precipitate at HIGHER temperatures (unlike most other things) so trying to heat the solution will not fix the problem. Dropping the pH is the best way to go. Either vinegar or citric acid should do the trick. Sulfuric or phosphoric acid will cause additional precipitate to form. An easy way to test this is take some of the precipitate and strain it out using a coffee filter. Scrape it into a glass and add a little vinegar. If it re-dissolves you can scale up and use the vinegar/filtrate solution as a supplement.

My dirt is heavy hard clay with a heavy Bermuda grass lawn. I cut out the bottom of the pool and left about 18 inches of the bottom attached around the edge, otherwise the the sides will kick up and everything run out under the sides. After I filled it up, I realized too late that I should have turned it inside-out, so that the pale blue inside would have been the outside. I've sort of grown fond the the little fish on the sides now. ;-) I grew the tomatoes like this last year with just compost. The compost held lots of water bit it still dried out really quickly once the vines got big. Before I set out my plants, I added three 25 pound bags of Wal-Mart Special Kitty Natural Litter to each bed. I scattered it on top and then scratched it into the top bit of compost, and it has settled further in as I watered each time. It holds tons of water and the extra water retention has really helped this year. I had a few determinant tomato vines that had finished fruiting, so I replaced them with some new transplants about a week ago. The roots had gone at least 6 inches into the underlying clay soil. Before I filled the beds last fall, I mowed the grass as short as I could cut it, I then covered the turf with 2 layers of flattened cardboard boxes to smother the grass. The worms and microbes had left no sign of the grass or cardboard in only 9 months. My basil and peppers are about 3 feet tall now. I'm permanently disabled and live on Social Security, so I was looking for something for raised beds that was really, really cheap. Cedar 1x6s lumber would have cost me about $100 for raised beds that were 16 sqft. Before I started using these pools I was growing tomatoes in 5 gallon buckets. The 6 foot pool is 15 inches deep, which is almost as deep as the buckets, but gives more horizontal space as well as roots going down into the soil underneath. If you've got some space and not much money, I could not recommend the pools enough for raised beds. I was not sure at first if the round beds would be a problem, but the really work well. On Victory Garden recently they showed a community garden in San Franscisco where they used straw-filled burlap bags to form the border of their round raised beds. There is a picture below. They were really nice because you could knell or sit on them to plant, weed, and harvest.

I'm not that worried about cost, but each of us has their own methods. I grow many acid loving plants and found the acidification of water with controlled amounts of fertilizer worked great for my cacti. I soon adjusted to all my plants. Results have been spectacular. I use kelp to add the trace elements. If you wish to learn more check the article out. Here is a link that might be useful: Ammonium Nitrogen and Acidic Water for Xerophytic Plant Growth

Math Error in First Post added Correction. The TDS in Foliage Pro Solution must be much higher than approximated. Edit: Math Error 1tsp= 4.94 ml 4.94grams at sp=1 1US Gal = 3.785411784 liters (0.18)*(4.94g/4)/3785= 235ppm Error Should be (0.18)*(4.94g/4)/3785= 58.7ppm at conversion factors of 500 ppm/mS or 640 ppm/mS 58.7ppm/500= 117uS or 58.7ppm/640= 91.7uS Too Low to be accurate "Edit: Math Error 1tsp= 4.94 ml 4.94grams at sp=1 1US Gal = 3.785411784 liters (0.18)*(4.94g/4)/3785= 235ppm Should be (0.18)*(4.94g/4)/3785= 58.7ppm at conversion factors of 500 ppm/ms or 640 ppm/ms 58.7ppm/500= 117uS or 58.7ppm/640= 91.7uS Too Low to be accurate "Not sure I'd have been comfortable with the assumptions behind the "total" ppm approximation" You were Correct on that Maybe others that use Foliage Pro can validate the EC readings with other meters. Even at 320 grams/Liter 1/4 tsp/Gal gives only about 105ppm total concentration. This is about 164 uS at 640 factor.