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pH level in pot resevoirs

This is a discussion on pH level in pot resevoirs within the Semi Hydro / Lights / Greenhouses / Accessories forums, part of the Orchid Culture category; Posted this on another site and figured I would pass along here. Wondering if anyone ...

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  1. #1
    jono is offline Junior Member
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    Default pH level in pot resevoirs

    Posted this on another site and figured I would pass along here. Wondering if anyone else can take readings and postulate about the information, growing, etc.

    From what I understand about straight hydroponics, pH in the water is *very* important, so I'm going to do some tests (with freshly deflasked seedlings at different pH levels) and will post the results. But first, here are some readings-- I may post more as time progresses.

    Readings taken at 2000 today, no rain

    Tap water: 8.5 pH w/ 90 TDS
    Fert mix (fox farm hydro food, kln, superthrive) : 6.9
    Resevouir in a couple oncidium pots: 7.5
    Resevouir in paph pot: 8.11
    Resevouir in phal pot: 8.5

    Not sure why my readings are so high (or why my tap water is that high). These plants are at most 2 months in s/h, many less, not sure if that has something to do with it. I'm going to try to pH down all these things to get down around 6.5 or 6 if possible. Some people suggest 5.8-6.2 is the proper pH for most hydro or s/h orchids. Does any have more information about the proper pH, research, etc? With regular hydro, it seems imperative to have the proper pH to allow feeding.

    BTW, all my plants are going gang busters in the hydro rocks -- it's truly insane how much they are growing, how large the new growths are, how healthy the roots are, etc. Most people seem to think the roots of plants in bark look healthy until they see the roots of a s/h plant -- then they are stunned and sometimes realize they haven't really seen healthy roots and most bark roots -- no matter how well cultured -- don't really look that healthy anymore...

  2. #2
    LJA's Avatar
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    Wow, your tap water's pH is through the roof--you could use that for marine aquaria! Is your tap water what you're using in your semi-hydro?

    I think you might be overly-generalizing about what pH is suitable for S/H growing--that's going to depend hugely on the type of plant.

    Don't do a drastic pH shift--gradual changes down would be much better. Here, I buffer our fert solution to 7.0 and have very good results.....

    What genus of seedlings will you be conducting the tests on?

  3. #3
    jono is offline Junior Member
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    Quote Originally Posted by lja
    Wow, your tap water's pH is through the roof--you could use that for marine aquaria! Is your tap water what you're using in your semi-hydro?

    I think you might be overly-generalizing about what pH is suitable for S/H growing--that's going to depend hugely on the type of plant.

    Don't do a drastic pH shift--gradual changes down would be much better. Here, I buffer our fert solution to 7.0 and have very good results.....

    What genus of seedlings will you be conducting the tests on?
    The seedings are bulbos, about ready to come out of the flash actually.

    I just took another tap water reading, letting the water run for 2 minutes before pouring a cup. pH is now: 8.9

    But, I have seen a fair amount of research that does indicate hydro plants have the best nutrient intake a pH 6.0. I think I'll try to get down around there, but the testing with the bulbos will probably help (at least for bulbos). I'll take it down slow though, that sounds like the best idea.

    In case you want to look, the annual water quality for the east bay, San Francisco is here:
    http://www.ebmud.com/water_&_environ...t/2003_wqr.pdf

  4. #4
    Cinderella is offline Senior Member
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    Louis, here is the water report for our area. Looks like our pH is not much better. I get salt buildup sometimes on my clay pellets. What would you do about that?



    pH - 8.2

    Calcium - 44 mg/l

    Sodium - 14 mg/l

    Calcium Carbonate - 145mg/l

    Magnesium - 10mg/l

    Alkalinity - 67 mg/l

  5. #5
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    Debbie, there's not much inexpensive you're going to be able to do to get rid of "hard" water. (Whatever, you do, don't use a "water softener" machine that uses salt or you'll kill your plants.) You can try getting a reverse osmosis unit, or watering with distilled that's you've buffered and added nutrients to, or you can collect rainwater and use that. (I say buffered with distilled water because the pH of it can drop drastically in a matter of hours. Pour some distilled water from a brand new jug into a bowl and let it sit out; CO2 and Hydrogen from the air will dissolve in it so rapidly that it will go from pH 7 to 5.5 in next to no time at all.)

    Aquarium stores sell products that raise and lower pH, so you could try those, but that won't help with the calcium carbonate coming out of solution on your S/H media or the leaves of your plants. The leaves can be wiped off with milk to get rid of the stains if you're getting any, but that's about it.

    The first few years I grew orchids, I watered with whatever was available out of the tap. I still do, but we're very fortunate to have water with a very low dissolved solids content. That, of course, means that we can get wild pH swings depending on the season and rainfall. While your water quality could be better, it's not as bad as some I've seen or used. All orchids will undoubtably do best with the purest water you can give them, where you've added trace elements in yourself. But unless you're trying to grow some species things that demand pure water or else :toofull: , most of the commoner things--hybrids--will grow and bloom with decent tapwater, and yours is decent. Water quality really becomes an issue when you're trying to get that last 20% of what's possible from your plants, but doing that is going to take more effort in terms of hassle and equipment than most people are ready or willing to commit.

    Jono, I'm very curious to see what kinds of differences you'll find in your seedling growth rates, so be sure to post back when you have some info.

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    Cinderella is offline Senior Member
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    Thank you, Louis. So what do the people with really bad water quality have?

    I didn't quite understand what buffering the distilled water meant.

    If I use distilled and MSU fertilizer, would that add back the necessary nutrients? I'm sure others must have this same situation....

  7. #7
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    Yes, you must use a fertilizer like MSU if you use distilled or reverse osmosis systems to water with. My sister in Colorado has to add MSU as her tap water is depleted of just about everything. I think she said her water will actually pull the calcium out of what she waters it with. I am not an expert on water but after she started using MSU with every watering she has noticed quite a difference.

    I am lucky as my water has a good amount of calcium and magnesium in it and I could get away without ever having to use that in a fertilizer except on plants that do well with very high cal/mag fertilizers like many Paphs.

    Many people in Southern Calif use a reverse Osmosis and mix it 50/50 with tap water. As well as mixing rainwater with tapwater.

  8. #8
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    pH is a measure of free hydrogen ions in a solution. Dissolved solids in water can "capture" those hydrogen ions and hold onto them. Pure water like distilled has almost no dissolved solids at all, so anything like CO2 that gets dissolved in that water will end up freeing a bunch of hydrogen ions. There's nothing to capture and hold them, so they lower the water's pH. The more of them there are, the lower the pH. The less of them, the higher the pH. A buffer is a type of "salt" (not necessarily sodium salt or table salt) that, after it gets dissolved in the water, will capture and hold those hydrogen ions at a certain concentration. Depending on what kind of salt it is, it will "buffer" the water in that it will keep the pH steady at a certain level. WIthout that, pH can swing wildly from high to low and back again, and that can be very detrimental to orchid health. Also, there aren't any of the trace elements and minerals in distilled water that living things need in order to survive.

    The MSU "Reverse Osmosis" formula puts those trace elements back into water that's been stripped of them (like RO or distilled). It will also buffer the water at a certain level (not sure what the pH of it ends up being since I don't use the RO formula). But in any case, you have to do that if you're going to use RO or distilled water exclusively, or your plants will just eventually die.

    Water quality is considered "bad" if it's loaded with dissolved solids or other molecules that can be unhealthy in high concentrations. If you use tap water, there are inexpensive inline filters you can install that will take out things like chlorine, iron, and other heavy metals, and just doing that can make your orchids grow better. Here, for instance, the greenhouse water supply gets passed through a carbon filter that removes the tap water's chlorine. The filter cartridges are cheap and easy to replace. At certain times of year, they dose our tap water with enough chlorine that you can smell it when you go to wash your hands or shower, and that's way too high of a concentration for my liking.

    Anyway, hope I didn't confuse the issue more.....

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    Cinderella is offline Senior Member
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    OK, so in another naive question....our fridge has a Cullinet filter that comes with the fridge and we change it out every so often. Would this water be preferable to tap? I have even heard that an inexpensive Brita Filter will get rid of some of the chlorine, etc. Which would be better...the fridge, Brita or distilled? Thank you!

  10. #10
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    Not naive at all.

    Our fridge has a filter too; but it's a carbon filter. I'm not sure what a Cullinet filter is, so don't know if that's any different.

    Brita filters use activated carbon to get rid of chlorine, along with little beads called Ion Exchange Resins to swap hydrogen ions for ions of lead, copper, calcium, and magnesium (among many others) in your water. The beads remove a lot more pollutants than plain activated carbon will. Just remember that, since more free hydrogen ions will now be in the water because of the ion exchange, the pH of Brita-filtered water is going to go down--get more acidic.

    So from your 3 choices, distilled will be the purest (and most expensive), Brita will be next, and carbon will be last, taking out the least amount of "stuff" but being the cheapest. Without doing any involved water tests, I would say that if you used Brita water in combination with a cal-mag type of fertilizer or the MSU RO formula, the vast majority of your orchids would be very happy.

    Carbon and resin beads do get used up though, so they need to be changed regularly to be of any use. Replacement cartridges can be high, and most people don't change them out anywhere near often enough to maintain their effectiveness. Reverse Osmosis units have come down in price quite a bit over the last 5 years, so if you have a large orchid collection, investing in one of those would be your best (and least expensive) bet in the long run.

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