Posts included in this FAQ are: LECA
L.E.C.A. High Ph?

Rockwool Dutch slab drip system
Mold on Rockwool

Other Best Gowing Medium?
sterilizing medium

Rockwool

Dutch slab drip system Posted by halfstep1320 04/02/05 @ 14:22

Hello all,
Newbie here. I would like some info on this if anybody has experiance using this method. I am planing on growing tomatoes, squash, and bell peppers. Whats better Rockwool slab or the Coco slab? I understand the concept, but do you need to cut holes on the undersides of the slab for draining like a "run to waste" system going to a waste reservoir, or just have a very low drip frequency so the nutrient builds up in the rockwool slab? Thanks

Response: Posted by: passiflorakae 04/4/05 @ 19:36:
hi there,
I preferred rockwool when I grew tomatoes and bananas. I had heard that coco slab was not as well-draining and that as it broke down little bits potentially could cause my tubing and emitters to clog- but I didn't use it so all I can do is pass on that rumor. It would probably be fine for an ebb-flow system.

With rockwool you set up your trays @ a 2 percent angle so that the trays drain toward your reservoir. You would cut a slit in the wrap on that end so the water runs out. If you let the water build up you'd drawn your plants via serious root rot. I'm sure if you went to a hydro supplier someone there would be happy to instruct you, there are also instructions on the web. Good luck!

Mold on Rockwool jtmerchant 1/ 23/ 05 @ 21:37: I have a flood and drain system and in a butter bucket is a bunch of LECA (clay aggregate) as a medium, with rockwool starter cubes containing tomato plants. On the rockwool are white dots, which I think might be mold. How can I tell if this is mold, and how do I get rid of it without upsetting my nutrient solution?

Response: Tony_K_Orlando 1/ 23/ 05 @ 21:49: If it isnt mold,it may be salt deposits, or water hardness or fertilizer residue.

It does build up on my systems too

joejoemomma 2/3/05 @ 21:36: If it is mold your humidity is to high. Try a humidity tester.

L.E.C.A. High Ph?

Posted by jtmerchant 01/ 5/05 @ 22:18: I am fairly new to hydroponics and for my first garden/hydroponics project ever I made a flood and drain system. Each pot is a cleaned butter container, with holes drilled @ the bottom and inside each butter container is a bunch of L.E.C.A (clay aggregate). After starting my tomato seeds in a different system (where the seeds were in rockwool cubes), I moved the cubes to the butter containers. Before this I checked the Ph. It was pretty high so I used my Ph down a lot. After about 50 drops of Ph down, I decided that I might as well try transplanting. So I moved half of the tomato sprouts to the butter containers. Now I realized that my water was a little murky from the LECA and so I checked the Ph. It was over 7.4. I put like 100 drops of Ph down, but I could only get it to like 7.1. It went back to 7.3 half an hour later. So I'm wondering what I should do, and if the LECA has high Ph. If it does, I should probably soak it then toss the water then soak/toss, then put in hydro system. I sound like a newb, but that's because I am one. Please help.

Response: hank_mili 01/15/ 05 @ 20:19: Sounds like something else is going on. LECA from what I've read is pH neutral.

willard3 01/19/ 05 @ 9:33: Are you measuring nutrient concentration? Nutrient concentration will affect Ph also. What is the Ph of the water you put in?

hank_mili 01/ 21/ 05 @ 3:56: Try this, put some of you LECA into a glass with some distilled water. Measure the pH. In a few hours measure it again. If the pH drops you will know you've got some sub-standard LECA.

MrGrowItAll 01/ 30/ 05 @ 11:00: Most LECAs are quite neutral. I use (brand name), and the guy I bought it from told me of leaving some in a sealed plastic container of RO water for over two years, and the water was 6.9 by his meter.

If the stuff wasn't fired properly during manufacture, there could be some leaching, especially from the binder used during pelletization (Aliflor used to use diesel fuel!).

akfog alaska 02/ 26, 05 @ 8:00: thank you MrGrowItAll i did not know that manufactures used stuff like diesel fuel, and will be cautious who i buy from.

Other sterilizing medium penjingguy 11/ 23/ 05 @ 14:48

After much searching of various problems I thought were nutrient related I found some pictures of tomato mosaic virus. The pictures matched as well as the symtoms. My question is can you heat lava rock and clay pellets to sterilize them? I'd hate to have to throw it all out. I know you can sterilize soil @ 200 for an hour or so , but will that kill a viral infection? How about 350 for 4 hours? I want the little viral suckers to die! Just like they did in my peppers and tomatoes!

Response: hank_mili 11/23/ 05 @ 23:24: Considering how lava rock or clay aggregate was originally made you can sterilize them without harming the medium. I once threw my lava rocks on top of a couple of sheets of aluminum foil on my gas grill. After 10 minutes I was pretty sure there were no parasites or anything else living on those rocks. Though I did not try it I was also considering using a propane torch with a fan nozzle on the rocks.

willard3 11/ 26/ 05 @ 9:25: All you really have to do is boil the medium to kill the pathogens. I have used expanded clay rocks for years and sterilize the used ones every two weeks in boiling water.

It's also good to use a soultion to remove mineral deposits left by nutrients on all stuff in contact with nutrients, including grow rocks. I use clearex every two weeks as well.

shelbyguy 12/ 22/05 @ 18:01: mix a little bleach with a little hydrogen peroxide and a bunch of water. rinse thoroughly

i dont bother sterilzing anything anymore. heck i dont even clean the stuff between grows. if you're getting deposits on the surface its because your tds/ec is too high.

hank_mili 1/ 2/ 06 @ 14:13: H2O2 and CL will react with each other when mixed.

Cl2 + H2O HOCl + H+ + Cl-
Cl2 + H2O2 ----> O2 + 2HCl

H2O2 alone would be more effective. I think.

cavemangardener (1/ 21/ 06 @ 17:51: I have run into trouble not sterilizing. Now I broil lava rocks in the oven.

My problem was that buckets full of lava went outside to dry on black plastic. I guess something that was wating the roots came back inside, as I got root rot for the forst time ever.

If you want to just replant, I have read of many growers watering the medium with and enzyme product that helps to digest the roots into matter the plants can take up.