Again, I don't know what to say, Jodi. My face got all red (yeah, I blushed) and I was really touched by your comments. I'm just really glad you're getting more out of your growing experience. THAT really rocks me. ;o) From Arjadiejai: Have you tried rooting cuttings in this mix? If I have a cutting that is important to me, or hard to root, I always stick it in a sterile medium like perlite or Turface. Strangely, I get the VERY best results from rooting in chopped sphagnum moss (not peat - the whole pieces of moss that were harvested live). The moss makes sense if you consider it's the medium most used in air layering. A mix of any combination of the three ingredients also works very well. If I'm starting cuttings and I really don't care about the strike rate, I use a soil made of screened Turface, fir bark, and crushed granite - the same soil as above. I screen it so particles are all larger than 1/16 inch so there is almost NO perched water to rot cuttings. By doing it that way, I can start the cuttings in larger containers and not have to worry either about a setback from potting up soon after the cuttings strike, or about overpotting and the accompanying saturated soil. In short, cuttings root fast and you can save a step because of a larger soil volume, but again - if the cuttings are important, use a sterile medium - it's the bark that could harbor rot organisms. About the cacti and succulents, if you water your typical tropical houseplants every day or every other day, how often would you water the cacs & sucs in comparison? It varies. I have caudex forming succulents that get water once/week in winter (they're under lights in winter), and every other day in summer (outdoors/full sun/clay pots). The plants in plastic pots get watered less & the ones in clay pots get it more - you know how that goes ..... I/you just develop a feel for what is needed & when after a while I guess. I kind of have a calculator in my mind that factors in how hot it's been, how windy, how much sun, how big the plant is in relation to the pot size and soil volume ..... and I decide based on that. With succulents & cacti, if I'm in doubt, I usually wait. To answer your question directly: It varies, but the interval between waterings is about twice as long - all things being equal. Also, have you ever ventured into terrariums? Would you use a mix of this sort in there? I haven't done terrariums, but I worked with a guy to develop a soil and fertilizer program for his. I think he was doing them to sell, and I might even have sent him some soil to try, I don't remember - I talk to a lot of people off forum about plant stuff. I didn't save his e-mail addy, but I talked quite a bit with him on a thread over on the Container Forum. I might go over there & see if I can look him up & find how he fared, but only if you're interested. ;o) Al

They sell rocks with painted faces, glue on eyeballs, and give them names. Yes you cam sell anything. Someone even bought a piece of left over food from someone else's thanksgiving dinner on e-bay for a outrages amount of money. You create it, someone will buy it (provided you make it sound as if they need it). Fact is you don't need a PPM,TDS, or EC meter to grow plants hydroponically. Though you probably wont hear that from a hydroponic supply retail store, because they want to sell you stuff. First you should understand the capability's of the meters to understand why. EC meters (electrical conductivity) TDS metwes (total dissolved salts/solids) PPM meters (parts per million) All of these meters do basically the same exact thing (just using different measurements). All of them use electricity to find out the electrical conductivity (EC) of a liquid, and give you a number from that reading. The nutrient solution is made up of many mineral elements, and not one of these meters can tell you what your nutrient solution is made up of. You will often hear people speak of there water supply having a certain PPM to start with. That is because unless it's distilled water it will have some elements in it (even if it is filtered). Again none of these meters cant tell you what's in it, or in what quantity each element is in. Not even if they are desirable elements or harmful ones. If you want to decide when to change the nutrient solution simply by the EC/TDS/PPM readings. The answer is simple, you never need to change the nutrient solution. All you need to do is adjust the readings by adding more nutrients to raise the numbers, or just add plane water until it's diluted to the range you want. Doing that you can keep the nutrient solution within a specific range indefinitely (even 20, 30 years if you wish). But here's the problem, as I mentioned not one of these meters can tell you what's actually in the liquid, and/or how much of each there is. For the nutrient solution to be beneficial to the plants, all the mineral elements within it need to be somewhat in balance. But plants don't absorb the all the elements within the water in a balanced fashion, they use only what they need, and leave the rest behind. This creates an unbalanced solution. The farther unbalanced it gets, the more the elements the plants are using in larger quantity become depleted, and faster than the other elements (thus unbalanced). Because some elements were used, that will drop the EC/TDS/PPM readings. The simple fix is to add more nutrients and bring up the readings to the acceptable levels again. This would work except that as I mentioned, the elements the plants don't use were left behind, and by adding more (balanced) nutrients to the solution, your also replacing more of the elements that the plants didn't use in the first place. So you still wind up with an unbalanced solution (even when your meter readings are in the correct range). Too much of this leads to the elements the plant isn't using building up in the nutrient solution, to a point they reach toxic levels. Your meter is just telling you the total amount of elements in the water. So you wind up with toxic levels of some elements, and deficiency of others, but together they add up to the right number of elements in the water. The meters simply cant tell you PPM level of: Nitrogen (N) Potassium (K) Phosphorous (P) Calcium (Ca) Magnesium (Mg), Sulphur (S) Iron (Fe) Manganese (Mn) Copper (Cu) Zinc (Zn) Molydenum (Mo), Boron (B) Chlorine (Cl) There's just no way for the meters to tell you which elements that are lacking, or which are in excess. If you need 3 oranges, 3 grapes, 3 lemons and 3 limes, for a total of 12 to make your recipe work. It won't be the same with 6 oranges and 6 lemons for the required count of 12. Even if they could tell you which specific elements to add, you still would need to have individual mineral elements in order to replace just what's lacking. Using Pre manufactured hydroponic nutrients (that contain all elements in a balanced recipe), that's not possible. The reason you cant find charts, or step by step how to know, or an understandable formula on when to change the nutrient solution, is because they don't exist (for the reasons I mentioned). There is just no way to tell what is actually in the water (nutrient solution), or the levels of them based on EC/TDS/PPM readings. The best (creditable info) you'll find on changing the nutrient solution or PPM levels will be based on specific plants, and related to the growth stage the plants are in. Even so, there are still many environmental conditions (light, temp, humidity, etc.) that will affect how your plants absorb the individual elements in the nutrient solution. If anything they will be just a guideline, and assuming your nutrient solution is within a balanced range. In fact any chart that you may find should have the disclaimer that they are assuming the nutrients in the solution are balanced at all times. Which is imposable to even guess, unless you change them regularly (or have a lot of money to have a lab test it). Think of a EC/TDS/PPM meter as just a tool that's a little more specific in telling you the relative strength of your nutrient solution (relative because it cant tell you specific levels of each mineral element) than would be if you are fallowing the manufactures mixing directions. But it doesn't matter what the strength of the nutrient solution is if it's not balanced. Anymore than it matters that the nutrient solution "IS" balanced if the pH is out of range. There are many rules of thumb on when to change the nutrient solution, and every guarder eventually figures out what works best for them. Everywhere from once a week, to once or twice a year. Things like the size of the reservoir, temp, size of the plants, the growth stage the plants are in, etc. all affect their decisions. Personally I change mine somewhere between once a week and once a month, again depending on the variables (including abnormal pH swings). But I rely mostly on observing the plants themselves. I look for singes of discoloration, and growth slowing down (that isn't related to environmental conditions like light and temp). Bottom line, I rely on observation to let me know when to change my nutrient solution. I don't even own a EC/TDS or PPM meter, I have a lot more useful things to spend $100 on. If you are not sure and want a guideline, start by changing them once a week for a month, then go to every other week, then stretch it out to three weeks the next month (and so on). All along observe the plants, look for signs of yellowing (dark green leaves turning to light green), growth slowing down, rapid or frequent pH swings. As long as you already have it use the meter to keep the relative strength within specific range, that will also aid in the accuracy of the experiment. Within a few months you'll be able to predict when to change the nutrients before you need to. Once you get a hang of that, try using stronger and/or weaker nutrient solution strengths, and again observe the results. "Do different plants have different levels of ppm they respond to and react to?" I don't usually post this, but this page/s was created for that very question. Keep in mind that EC/TDS/PPM is just the relative strength of the nutrient solution, the numbers really only refer to a stronger or weaker nutrient selution. And as always it also assumes that your nutrient solution is always balanced. ph/cF/EC/PPM Levels for Fruit

Would like to add and correct a few things here: 1. Pure water without any dissolved solids does conduct electricity pretty well, (try to put 110 or 220 volt in recipient with 100% pure and distilled water and put your hand in there!) the difference is that, the more dissolved solids that are dissolved in the water, the higher the conductance of the water. 2. Lots of talk has been done about PPM conversion rates that are based on electrical conductivity EC reading of mS/cm but converted to various PPM rates, mainly 500 or 700. Do they correspond to actual PPM of any nutrient solution, or not, are they related directly or not, how comes etc. I guess many people haven't understood why and how it is. It's simple: The actual ppm value of a specific sodium chloride solution is very close to half of its conductivity value (in microSiemens/cm), That is why these "TDS" meters display the conductivity as an equivalent NaCl amount (1000/2= 500). The 700 conversion rate is derived from a specific potassium chloride (KCl) solution instead. Important: both ppm readings of either conversions used here are not related directly to YOUR or ANY nutrient solution or their actual and total PPM content in all elements. Hence, never think that a ppm reading of any TDS meter expresses any actual ppm of your formula or solution nor can be compared to any ppm recommendations for single elements as in N= 180 ppm, or P= 250 ppm etc. BUT it happens that the reading of a 500 conversion rate TDS-meter is quite close to most nutrient solutions, generally the reading is 10-25% higher as the actual content in ppm. It varies with components used as in the actual composition of the nutrients. Fortunately or unfortunately, however - do not confuse the ppm reading of any TDS meter with the exact content in ppm of elements in your nutrients or the total dissolved solids it contains. 3. As for the use of ppm readings and data (of a so called TDS meters), you may pretty well state ppm readings and data in forums as long as you know and TELL the conversion rate that goes with it as well.

"The relative part (single elemental data) using ppm as a unit, can only be communicated between people who are able to understand ppm data in a nutrient formula." It is not a mater of understanding the ppm data, it is a mater of measuring it. If you know exactly what you put in it (when it's fresh) then it's not a problem. If you are using a commercially manufactured nutrient, then you may be able to figure it out (when it's fresh). But weather you manufacture them yourself or use a commercial nutrient there is no TDS, PPM or even EC that can measure them and brake it down accurately after that (or even then). That's why they are all just a relative measurement regardless. I can give lucas that all the meters start from electrical conductivity, they are electronic devices after all. But that does not change the fact that none of them can tell you exactly what is in a solution, just give a total reading. Lets say there was a meter that did break it down into individual elements, that would be great, right? Most manufactured nutrient solutions are a 1,2 or 3 part nutrient solution's (and are what 90% of most growers use). How does it help to know a solution is lacking, lets say Magnesium? Not much because unless you can just add the lacking Magnesium (not possible with pre-manufactured nutrients), then it's kind of pointless. You will still need to change the solution in order to maintain a balanced nutrient solution. zathras I'm interested in the 'ICP mass-spec" that you mentioned. I have never herd of it, sounds expensive. Do you have any links to what you are referring to, I'd like the check it out even if it is expensive?