Can you use red lava yard-rocks for grow medium ?

Discussion in 'Hydroponics' started by grow4fun, Feb 2, 2006.

  1. grow4fun

    grow4fun Registered+

    I’ve heard people mention ‘lava rocks’ as a grow medium, instead of Hydroton. Are they talking about special lava-rocks sold at a grow store, or the red lava-type rocks used for landscaping, that people use in their front yard in place of grass ?
    The yard kind is probably very cheap compared to Hydroton (they probably sell it by the cubic yard like soil). What I wonder is:
    1) does it release minerals into the solution that would raise/lower the pH ? and
    2) does the rock being red mean it’s got a lot of iron in it, which is toxic to plants (except in micro dosages) ?
    Has anybody grown in red yard rocks?
  2. MaryjaneMenehune

    MaryjaneMenehune Registered+


    I do not know exactly what hydroton is, but i think you might be referring to rockwool or a brand name associated with rockwool... rockwool is available by cubes as well and can be purchased on ebay occasionaly. Most of the stuff specially formulated for high performance is just a tried and true thing tweaked slightly, you may find out, upon a little more research into some forums, about the differences if any... i hope this can be of some use.
  3. NugsNjugs

    NugsNjugs Registered

    Whats crackin all?

    OK, if your gonna use red lava rock from your yard please put it through a serious bath first, soak it in PH'd water (5.5), then run it through your stove for 30 minutes to kill the crap from your yard.

    Hydroton is basically expanded clay pellets that in no way compare to rockwool. Hydroton I believe is a brand name.
  4. BloodShot420

    BloodShot420 Registered+

    I use hydroton in my DWC... i must say - it works awesome, but its a bitch to clean.

    it will not change the ph of your water... and they are small, and pretty light... they wont crush your plants, or cut them - even seedlings...

    hydroton gets my vote.
  5. turtle420

    turtle420 Banned

    Sounds like good advice to me!

    As to the lava rocks, the ones I'm using are your typical Home Depot BBQ lava rocks... just crush them a little bit so they aren't that big, and just use them. Definitely you HAVE to wash them before use. But they're good for that purpose.

    There are some people that preffer lava rocks to Hydroton Pebbles, as the pebbles might shift and cause excessive stress to the girls' roots. In any case, to each his own. NugsNjugs' advice is good!


    -turtle420 :cool:
  6. BloodShot420

    BloodShot420 Registered+

    I only fill a 6" netpot with hydroton... i'm not sure how they would hold up to a big E&F tray... I was thinking about trying it this summer.
  7. grow4fun

    grow4fun Registered+

    Wow, barbecue rocks. Never seen those before. Thanks. They look better to me than clay pebbles. I am still interested in the use of landscaping rocks (I would clean/sterilize them of course). Larger volumes of them would be way cheaper [than barbecue or hydroton].
    People tell me their experiences with [something], but when I do my own experiments I come out with completely different results. For instance Hydroton. “It doesn’t affect the pH of water”. In my experience that statement would be true only if you’re using tapwater, where the pH is already high 7.2 – 8.2. I washed my hydroton a dozen times. Then immersed it in a volume of pure R.O. water (pH 6.2), waited overnight, and it invariably raised the reading to around 8 – quite unacceptable. Tried it several times. Good pH meter, tested, calibrated; a solid experiment. And no matter how many times you wash them, more red powder keeps coming off – you could wash them until they disintegrate!. Guess I could do what other people do: use pH down and get over it.
    Maybe there are different brands of pebbles. I’ve read that some ‘cheap agricultural’ brands do leach and raise the water pH. I got mine from a growstore, but maybe that brand has started using the cheap stuff. Or maybe it’s all that way………
    Last edited: Feb 3, 2006
  8. Da1KrayzieThug

    Da1KrayzieThug Registered+

    I believe lava rocks might have nutrients and other materials stick into their structures and might get released later. I'm not sure about this but if lava rocks really do some from volcanoes then I'm sure they would have something in them that might make pH or ppm level fluctuate later on. I would just stick with the hydroton and stay away from the rockwool since Zandor hates it so bad for the same reason I think lava rocks might be bad. Goodluck <3
  9. latewood

    latewood Banned

    hey carolina boy...look here, lave rock is usually added to the bottom of the pot in so9il plants to increase drainage...If you tried to use it in dwc/hydro it would work, I think but, you would not hold moisture as much, It won't hurt anything, and I think it's red, because they call it 'lava rock'...hydroton is the shit...It is reusable and provides anexcllent medium for hydro...Imho.lw
  10. latewood

    latewood Banned

    This is the thing to do with yard rocks and soil, if you choose to dig up your own medium...
    This is good advice.lw
  11. skunkydelight

    skunkydelight Registered+

    lava rocks are just have to wash them with a 10% bleach solution and they will be good to go...they let the plants anchor very well as opposed to hydroton which moves around under pressure of large base roots...
  12. Gen

    Gen Registered+

    I'll have to go with skunky on this one. I have hydroton rocks and yes they do shift very easily. I would go with lava rocks for the same reason skunky posted.
    They also hold beneficial bacteria well too. Next grow I'm going to try lava rocks. Only problem is I have this HUGE bag of hydroton.
  13. skunkydelight

    skunkydelight Registered+

    Gen, I'm in the same situation...I have a 20LB bag of growcubes that I'm not gonna use either...btw, you don't dig up lava rock, that would be silly. They have huge bags of it at Lowes/HD or any homefix store for dirt cheap....check it out! You can crush them up a bit if you think the peices are too big as well...
  14. latewood

    latewood Banned

    lava rocks need to be crushed up, before using...but, they don't hold a candle to hydroton for hydro...
    which, I have cleaned and rinsed and never get dust after I'm must use a collander or something that allows the dust/redness to dissipate over several rinses, it works...Zandor uses one of those homeowner portable cement mixers w/a shitload of holes drilled in the sides and hoses'em DOWN...

    goodluck, be patient and on task always, when growing. Try and start small. but use good proven products and techniques until you get a 'REAL' harvest or 2 under your belt.
  15. Gen

    Gen Registered+

    20 lb bag of grow cubes. That's hilarious. I'm still trying to think of ways to use all of this hydroton. I may just end up dumping the stuff in the garden. Grow cubes. Well, some people swear by them. I tried the jiffy pellets and a bit too wet for my liking.

    I'm trying your cloning method in a glass jar. I put 2 clones in a glass jar. Sprayed the cuttings and put the lid on. I layed the jar on it's side and put it under a weak light. The plants started to curl. The stems turned into a C. It's been 3 days. The stems are brown around the cut portion. But they don't look rotted. The rest of the clone is healthy and green. I don't see any root bumps. Hope I'm doing this right. I know you put a container inside another container. But I tried something different.

    I know what you can do with your growcubes string them together for Xmas decorations.
  16. Herbus

    Herbus Registered+

    Hey all, just wanted to add something to this quote. Lava rock once it cools, as it ages turns from red to black. It can take hundreds of years to make this change. The darker lava rock is the better it is for inert applications. Very dark or black lava rock is non-toxic (and inert) it is normally more expensive then the red because it is normally below the red in the quarry and more difficult to collect. All aged lava rock is PH stable. Black lava rock is just as good as any other hydro media. Red lava rock is not. Red lava rock can still has trace sulfer compounds that when wetted can cause excess sulfer dioxide. Although sulfer is a trace nutrient in most nutes mixes - excess is toxic to plants.

  17. turtle420

    turtle420 Banned

    That, is some very interesting information. Thanks for sharing Herbus... very, very usefull.

    I'll try and get some of them black aged lava rocks... ;)
  18. ICEToker

    ICEToker Registered

    the idea of using rocks is to support the plant roots, but not to absorb water...
    Hygroton is a brand name...they work very well...I use is a bitch-a-roony, but do-able...{baking in oven for a little while works wonders}...
    Hygroton is very smooth and lava rock is generally rough and porous...I've heard it said that the rough rock has more to grab onto...I've never had a problem with Hygroton...I also use rockwool cubes to start seeds and clones, I love it also...I dont grow in rockwool only because it holds water too long, but it does fine for clones and seeds...
  19. Herbus

    Herbus Registered+

    Now just a quick comment on this posting. Hydroton is expended clay pellets it is the most porous surface currently available for hydro growing. I can't use it because it floats when I flood my system instead I use regular natural aquarium gravel. I don't use rockwool anymore as it raises the PH at the root zone and in my experience has slowed growth. I think sometimes we get caught up in media - media just holds the roots - the difference is the frequency of watering needed to keep the plants growing at the maximum rate, and how easy it is to remove the excess nute build up that reusables have. Aquarium gravel holds water for a short period of time 4-6 hours depending on the size of the plants. Because of this short period less water has a chance to evaporate on it's surface and so less excess nutes are left behind to spoil future crops. Very practical only requires rinsing between crops. Both hydroton and lava rock will have higher risidual nute build up because of the relative porosity of both. Baking it will only make this problem worse over time. It is however still an excellent media for a while, and in fact you may never have a problem with it.

  20. Silver Balls

    Silver Balls Guest

    I heard mixing lava/vermic to 4 to 1 ratio is great to, but I am a first timer, listening to advice. Also, something about using vermic at the top inch or so being it tends to wash down after flushing. HELP !!!!

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