Experiment: Perlite VS Lava Rock

A while back I thought about an alternative to perlite as a soil aeration substitute.
Clever me (insert sarcastic cartoon sound here), didn’t want to buy another bag of
perlite because I’m a cheap prick so I thought about lava rocks. Unlike perlite, I can rinse off and reuse pumice stone in short order after a successful grow.

So on this attempt I’m taking 2 identical seeds, Strain and origin is unknown so they make for prime contenders. I’m NOT going to experiment on quality seeds like the
bunch I picked up from ILGM, so these will do.

I bought some really impressive street crap a long while back and the buzz was very KILLER. Tasted like crap but the effect was very very impressive. Lucky me there were seeds in this bunch and I certainly picked out every one I could find to stash away and try to grow later.

So here we are, making a run at that experiment.

Unknown Strain and origin.

Indoor grow, Mars Hydro 2.7X2.7X63 tent

CLW 450 COB LED & Carambala 600w Full Spec LED

Fox Farms Ocean Floor soil

Cloth 3 gallon pots

I named the plants for easy comparison.
Meet Ronny and Rita the regs. (Regs= regular non specific street green)

Ronny has a soil pot filled with about 25% - 30% 1/4 Pumice stone for aeration
and Rita has 25%-30% Perlite mixed in.

The theory = With a greater surface area, I’m hoping that Ronny had a better
environment to grow an impressive root ball. More room for air, more room for root anchor, a solid porous zone for Myco to grow and thrive and a much heavier pot.

Both plants have a dose of Great White at their root base, both plants will be under
the same light. Both plants will be getting the EXACT same watering and nutrient
solution of 1/4 power Dyna grow and Dyna Bloom. (not until the 5th or 6th week to start). Will be dosing each plant with pH’ed water @ 6.5 - 6.8 with Rhino Skin every
3rd watering. Will be giving the soil a feeding with Myco chum one week before the
flowering switch.

I think this will be fun to watch and see what happens.
Keep your fingers crossed and wish me luck!
Oh my! It’s FRIDAY!!!
Hope everyone will have an INCREADIBLE weekend
and take some time to relax and spend time with a loved one
OR treat yourself to some peace and quiet.
Best wishes and regards


Hi Phil-- im watching ur experiment!! U have a great weekend too!


Going to watch this as well. My Canna soil retains quite a bit of water and I was thinking of using it in the same way. Did you layer it or just mix it through the soil

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I have full sized lava rocks at the very bottom for drainage. The first 1 &1/2 - 2 inches is the
full sized rocks, I mixed in thoroughly the pumice stone as you would the perlite,
I filled the pot half way then used a glass jar to as a mold, filled in the rest of the pot with
the pumice and soil mix. Then when ready to transplant I pulled the glass jar (it was a thin
jam jar) which gave me a nice plug to fit the roots into.

The pot is noticeably heavier than normal. Same percentage of pumice stone adds about
3-5 lbs to the equation.

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The lava rocks i have are only about 1/2 inch. I was going to mix them like perlite and see how it goes. Just feel my soil is too retentive :slightly_frowning_face:

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That’s only 50% bigger than the 1/4 pumice I bought so I don’t see why it wouldn’t work.
Sadly I can’t fast forward time and give you a definitive answer. If you have junk seeds and
can spare the soil and time, go for it. If you want to sit back and wait for my experiment to
fail or succeed that’s cool too. I don’t mind being the guinea pig.

Either way, rock on bro. I’ll update this journal once or twice a week to satisfy any curiosity
that might exist.

Have a good Sunday bud.


I’m set to watching. I have spare seeds there and will drop them towards the end of December, be interesting to see how it goes. Take care and thank you Phillyrock

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@PhillyRock nice experiment!! Set to watch! Stay Safe and Lit My Friend!!:fire::fire::fire::v::v:

I have to make a correction in my post.
I stated that I was using a CLW 450. My brain was mush at the time of posting.
The correct light is a California Light Works Solar Extreme 250.
Still using the Carambala 600w but will be switching to a 300w UFO
Pink 4000K diodes, deep red and IR diodes 309nm - 495nm for UVB,
Another test within a test, But that’s a little while out.
Only switching at flower period.

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A few days have passed and things are looking promising.
Ronny= Yellow tag
Rita= Green tag

The first watering was yesterday and I’m making sure to water around the perimeter
of the pot so the roots have to search for water. Can’t get root ball unless you make
them work for it. Next watering I’ll add 2ml of Rhino Skin Silica supplement.

This is my current grow, the two Rags seeds I’m experimenting on and
two ILGM Gorilla Glue photo’s.
I’m hoping they turn out as awesome as some of the other threads I’ve seen.
With the proper love and care I think I’ll be successful.

Next update in about a week.

Hope everyone has an awesome week.


I always see posts about “good genetics” and how certain strains are more resilient
than others. Well, I have the perfect example of bad genes and how crappy some strains can be.

As a seeds compare, I have two ILGM Gorilla Glue Photo seedlings looking green and lush
and two ‘Rags’ seeds that are growing explosively but looking like crap. They are not unhealthy but not the prettiest of the bunch.

Ronnie and Rita in just 5 days from previous photos.

Now look at the stretch marks on this plant.
Light is 28 inches above the plants. GG’s are same distance and not one bit of streaking.

I’m happy with their rate of growth but MAN they are two ugly broads!
(No offense to any women obviously. Just using a little tongue and cheek humor)


I just realized how crappy my photos from two days ago were.
I didn’t notice at first how the LEDs screw with my phones camera.
I’ll remedy that here in a second.

First observation in my experiment:

After preparing new pots for transplant, the soil is just tamped down using the lightest of
compression. After a few weeks I’ve noticed (last grow and this one) the soil seems to settle
significantly with watering. The lower the volume of planting medium, the smaller the root ball, in return the smaller the plant on top, the smaller the yield etc etc.

The pot with the lava rocks are maintaining the original volume a lot better than just soil and
perlite. If the roots have more area to occupy, the root ball will be bigger comparable to the
loss due to settling. I’ll be able to tell for certain at the very end.

Now to correct the Genes example I attempted to demonstrate.

This is what good genetics look like.
ILGM Gorilla Glue Seedling, lush and vibrant.

Poor genetics from random street swag.
It wasn’t an “all of a sudden” issue either.
This was a few days ago.

And this was today.
Showing it’s just poor breeding and lineage,


Water is a great compactor and that’s my main concern. The South Africans spray it to compact their roads during construction. I didn’t actually notice the stripes in your pictures until you said. I have the same issue (really badly) with my veg tent, not so much in my main tent with the hlgs though :sunglasses:. Interesting point with the genetics. Be good to compare the overall difference regarding size, height, yield and quality of the end product.

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I’m hoping it grows out and I get a chance to see what kind of strain or combination it is when it matures. I doubt very highly it will be identifiable because it’s probably a mutt of many different plants. Glad I have a dozen or so seeds because it was definitely a sativa majority buzz when I smoked it. Lazy feeling, calming, mellow but didn’t inhibit movement when required. I really enjoyed it.

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Since the start of this experiment I wanted to focus on one thing and one thing only.
Root health.
Of all the things here I’ve read on this forum as a NOOB (yes, that’s with capital letters
because my experience getting into this hobby was less than nothing, which is Nay-thing)
was “…focus on root health and everything else above the soil will be a success. Let the
leaves tell you want the roots need and stop concentrating on the top”.
My reference quote isn’t verbatim but you get the point.

The plants were growing nicely and gained some serious mass when I started to notice that
on all four plants (The 2 rag seeds involved in this little experiment and the 2 ILGM Gorilla
Glue photos I have in the same tent) were drooping about the half way point in the light cycle.
I dove into the interwebs and discovered the science behind “plant respiration”. I found an
obscure post on another botany forum (it didn’t specifically focus on cannabis or one plant
in general) that seemed to make some sense. The post was tied and pinned to a family of
plants (including cannabis) like mint, catnip, chamomile, hops, hackberry and cannabis.
Another thing I learned when diving into this rabbit hole was Elvis is alive and well, living on
Mars, buts for another time.
The article explained that when a plant has exhausted it’s absorbed supply of CO2 and
expended all the oxygen but converting the plants sugars, it will droop, naturally. That is what
is supposed to happen. BUT, in this article some green thumbed PHD mentioned that his
plants were on an altered light cycle of 8 hours of light and 4 hours of darkness twice a day.
The explanation was that when a plant has reached it’s relaxed state, photosynthesis is at it’s most sub-optimal level. This light schedule was chosen to increase ‘Up’ time on the plants.

So I decided to give this a try for the last 9 days, and today will be day 10.Actually, now it’s officially 10 days as I look at the clock and it’s after 12am. I have got to say I’m NOT in any
way disappointed. I’m impressed at the perkiness of my plants. Far better than my last batch
but I can’t attribute anything to that alone because more than a few mistakes were made.
However, with this lot, all four plants are growing at twice the rate of my last grow. The two
Frankenstein plants and the two GG’s from ILGM are all getting the same light treatment.

I’ll know in another week or two if is it actually is doing anything significant or it’s just me
making fewer mistakes than last time. I’m going to continue with this cycle until all four need
to go into bloom. I’ll keep updating and posting photos of the process as things progress.

Have yourself a good day tomorrow,
chin up guys and gals, Friday is less than
48 hour away. Godspeed and wish me luck!

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It will be interesting to see how this 8 and 4 light cycle affect yield :thinking:

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You may want to look into using a 6/2 light schedule. I have been using 6/2 for the past four grows with excellent results. The 6/2 schedule is for veg, I use 13.5/10.5 with supplemental far red for flower.

Here is a link to a recent grow update:


Here is a link to a post that roughly describes my light schedules:


Man, I can’t tell how badly I want to try this light cycle, but current situation is prohibitive.
I live on the 3rd floor of a residential home that was converted into apartments. When there
is a lot of activity on the bottom two floors the temperature goes up 10F-20F so I have to act
fast and trigger higher exhaust speeds, open a window or the opposite at night. Switching to
a 6/2 light cycle would have me waking up in the middle of the night or unable to leave for
work on time.

Also, with this current light cycle I can power down my electricity draw during times of heavy activity on the bottom floors. As tempted and alluring as your schedule and grow looks, and
as bad as I want to duplicate (or attempt to duplicate) your success, right now I’m kind of
pinched in the dork to try it. Had I known about this during the first phases of this stupid
lock down when no one was going anywhere, I would have done this from the very beginning.
It’s funny how things you learn AFTER the fact haunt you long after the opportunity passes
you by.

I’m going to start looking for an excuse and reason to attempt this in the furure if you don;t
mind me stealing your idea! (Yes, I plan on stealing this idea later, so I’ll be sure to give the
credit to you :grin: )


A few days ago I purchased the Apera PH20. I couldn’t rely on that garbage yellow stick
we all start out with. The readings I was getting couldn’t possibly be right, and with a new
grow just starting, an experiment in the works and two lovely GG’s from ILGM I wasn’t going to mess this up. So I dug deep into my pocket and bought it.

I recently started a thread about removing the Chloramine from my sh$tty public utility water
because it’s a worse than Chlorine. I found API and MAN I was excited. With the API added
and using Rhino Skin, my water was reading a constant 6.4 to 6.8 pH. No way was this right.
My yellow sh$t stick just has to be wrong.

After getting the new tester ( and finally getting it calibrated by watching a Utube vid) I tested
the same mix again. Rhino Skin, API and crappy municipal water, I almost pooped myself.
Three times in a row the test came back 6.7. There was no way this was right either? Right?
I tested about 5 different things and 2 different mixes and I’ll be damned, it was right.

So, long story short, I guess even a blind squirrel gets lucky once in a while. Or, in my case,
if you throw enough sh$t at the wall, eventually something will stick. Of all the things to get
right, having a ready source of pH correct water, in under 3 minutes isn’t a bad situation to
be in.

Yay me?

Tomorrow is Friday ladies and gents,
Have yourselves a great weekend.