other options include lava rock, granite and river rock. Don't be too hooked on "pea gravel" Call some landscape supply places or aggrigate supply and ask about quartz and granite in the 1/2"-3/4" range.
Don't be too hooked on "pea gravel" Call some landscape supply places or aggrigate supply and ask about quartz and granite in the 1/2"-3/4" range.
Hey there, TCLynx.
I see 1/2 -to- 3/4-inch river gravel (river rock!)
recommended everywhere I look,
but I'm darned if I can figure out the reasoning behind it.
Sylvia Bernstein and Murray Hallam both recommend it, of course,
and I get the feeling that most folks just repeat their advice
without understanding why.
I come from a cattle ranch in Colorado
where we grew 800 acres of corn and alfalfa,
so I tend to think of plants growing in dirt.
Now, I understand that dirt is not going to provide
the aeration and penetration of solids that we need,
but why not something like 1/4 inch gravel?
We have lots of that around here (we call it 'pea gravel'
and, being mostly granite, it passes the vinegar test)
and I would think it would provide much more surface area
as well as still allowing the solids to filter down
and plenty of air to circulate during the 'drain' cycle.
(the pea gravel passed the vinegar test, being mostly granite)
I'd think the seedlings might be able to grasp the bits more easily,
though I can't guess how the earthworms feel about it all.
I assume there's some magical information I'm lacking.
I don't want to just follow the herd,
but I also don't want to get it wrong-
Can you help me understand this?
This was a faulty attempt to repair the font in my response.
I'd delete it if I could find a 'delete' button...
I put a layer of lava rock, then a mix of hydroton and pea gravel and my plants are thriving, Carrots are really doing well in just 4" of this medium..
The recommendation for 3/4" gravel is generally to avoid clogging as roots and solids tend to fill the spaces between smaller gravel more quickly.
That said, I've been using 1/2" media just fine for timed flood and drain for years and it even works fairly well for siphon flood and drain but where the water enters the bed it is more prone to clogging up and needs to be poked with a stick more often that the larger gravel would.
Now 1/4" is going to be a bit on the small side and if you decide to use media that small you will want to take head that the water flow through small gravel is going to get slower and could give you some issues with siphons (as in you might be pretty limited in what size siphon will work just because the smaller gravel slows the water flow more than a larger gravel will.) You may find the smaller gravel clogging or becoming anaerobic far sooner than a larger media would. However, depending on the situation, it just might still work, no guarantees though.
I'd say your best bet is to go to your nearest yard/gravel pit and take a look for yourself and bring some vinegar to pour on the stones - if it bubbles, avoid it. But river rock is a pretty safe bet. Gravel pipe bedding should be inexpensive and worth looking at (open graded, low fines, round stone).
You asked about the uses of bell siphons and loop siphons - I have both types going in our house and could honestly recommend either of them. The loop siphon is extremely easy to set up - just make sure that the tubing is the right size - and mine has never skipped a beat. The loop siphon can also be made from standard PVC piping as well if you want. As the loop siphon is usually made outside of the grow bed then there are issues of algae growth in the hose - but if you cover the hose then this is no problem. I guess the loop siphons can be easier to set up and get your head around.
The Bell siphons also works really well and are fun to experiment with. I think that these seem to be more of a long term - in the bed - type of solution.
As I said, I use both type, really like both types, and have no trouble at all with either type - so I guess you should go with whatever floats your boat!
Thanks for the prompt responses.
I can see that the smaller rock is apt to slow water flow
and be a more efficient (not what we want) filter of solids.
I gotta tell ya, though,
I can NOT get my head around the idea
of direct-seeding into thumb-sized rocks.
Well, I hope experience is about to make a believer out of me :=)
You make a good point Shas. It is difficult to direct seed into large rock. I have much better success direct seeding my crushed brick, which is maybe 3/8 to 7/16 or so. That said, you don't need to direct seed for most vegetables and many actually do much better being transplanted. I went with my two media choices (river rock and crushed brick) mostly for holding power. They are both easy on the fingers, but fairly hard on the back when you clean and fill the first time. The rock was free (screened it with two sizes of wire mesh) and the brick very inexpensive. If I want to direct seed spring onions or carrots, they go in the crushed brick. The rock has proven itself through many tall and/or heavy plants. That's what I really like about it. Worms do very well in both in case you were wondering.
There are many materials which can be successfully used. That said, if someone offered me free hydroton (which I think is a great media) to replace my rock or brick, I'd politely say no thank you.
I wouldn't refuse free hydroton unless it was contaminated with something toxic. But I probably wouldn't replace all my river rock either. I might test out the hydroton on top and rock on the bottom or leave some beds rock and have some beds hydroton. And I would probably not replace, I'd just add more beds, but that is me and my strange aquaponics addiction.
As to seeding in big rocks, I can see how most seeds could bounce down too deep between 3/4" or larger rocks so that size might require more in the way of careful seed starting but most seeds I'm able to just sprinkle about in 1/2" or carefully place at the high water level. One trick is a scrap of tissue or paper towel to act as a wick and help hold the seed in place till it germinates and takes hold on it's own.
As I mentioned, I think it's great media. If someone did give a bunch, I wouldn't refuse it either...might trade it for a pump or a new GB... :)
I don't think it would it would be as effective in a few of my GB's. I've mentioned a few times the support factor. I'm actually getting away from the big stuff in the system in the future I think. I've got some really crazy indeterminate tomato varieties they go nuts in the system. They are heirloom seeds I ordered in the States and brought to Thailand. I've never seen tomatos grow this tall, or long as the case may be. They won't stop producing either. Have to drape them over the sides as they are well over 2 meters now. They, along with the cukes and a few others will find homes in wicking beds soon.
Not sure what the consensus is here, but I've found some seeds just don't do well directly seeded into the media. My cukes, green beans, peas, even tomatoes do much better when started. Even my lettuce, which I now start in a vermiculite/perlite mix (it's what the hydro shop here sells), seems to have a much better success rate when transplanted. Cabbage too. Ok, got one - my chinese radish (looks like a big, white carrot) and then spring onions do ok, though I often transplant the spring onions (I've been told you can't transplant them). My rock is under 3/4, say a little bigger than 5/8 in. I think actual 3/4 is pushing it a bit. Anyway, just another example of the many options you have in AP. I'm thinking it was on your page where I viewed some crazy media experiments? I thought it was a great example as to how we over-think much of this. When someone new asks, we give our personal favs and best advice, but the reality is that you definitely have options and most will probably grow veggies. Have to get the water right, but tanks, containers, media and much of the rest are fair game.