The carcinogen in DE and clay products is crystalline silica, a natural quartz like substance that is also in perlite, sand and many other products you probably encounter in daily life. There is only a trace of the stuff in DE. Breathing silica dust may cause silicosis or lung cancer. That's why you need to use a mask when screening and mixing any container mix. Touching the stuff won't hurt you.

Thanks for letting me know Ohiofem!

I was wondering if Pumice could perhaps replace bark in the 5-1-1 mix? I think it's suppose to hold water and wouldn't mold over in domed trays...what size should it be?

I had to laugh when I did a Google search on pumice. Turns out it has a high crystalline silica content. Don't get me wrong -- I think it's a great container substrate. But it's nothing like bark, so you might as well drop the idea of creating a mix "like 5-1-1" if you are not going to use bark.

I suggest you come at your question from a different direction and post it again. You want to know what to do to prevent mold from forming under the dome you put over your African Violets. In my opinion, the answer is to remove the dome and figure out a different way to deal with the watering demands of your AVs. My basement is made of concrete and it's a constant struggle to keep mold down if we don't run our dehumidifier full time. You don't need something organic to grow mold.

What's strange is that I had just regular soil with some perlite under my domes, and I had NO mold, only the bark mix plants had mold.

I decided I'd go with a form of gritty mix. Since my pots are so so tiny, I don't really need a lot of mix to begin with, what do you think about this mix on ebay?

http://www.ebay.com/itm/321195534067?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

32% - 1/4" - 1/32" Natural Cascade Mountain Volcanic Lava rock. Pleasing mix of red, grey, black and white.

32% - 1/4" - 1/32" Natural Cascade Mountain Volcanic Pumice. Pumice has many tiny gaps or air pockets that allow roots access to oxygen, nutrients and water. Pumice improves both water retention and drainage.

32% - Turface MVP. Turface MVP contain 26% solid material, 39% water-holding capacity and 35% air-holding capacity. This allows Turface MVP to hold water and oxygen ��" as well as nutrients ��" in nearly perfect balance, helping to produce fine root systems.

4% - Excelerite Remineralizer & Micro Organism Multipler. A broad spectrum of bio-active minerals and over 60 trace elements that are necessary for the well being of beneficial soil microorganisms.

I LOVE that it's pre-mixed! lol

LOL at the pumice with even more cancer crystals! haha I guess I'll just be wearing a breathing mask no matter what!

So what does everyone/anyone think of this mix?

I think particles down to 1/32" means that this mix can't really be considered "gritty", though I guess it depends what the distribution is from 1/4" to 1/32".

Maybe your mold issue had more to do with the particular bark you were using than with bark in general. I personally haven't found much success with 100% enclosed anything, but have done well with small vents, and by regularly opening up enclosed containers and blowing some fresh air inside daily.

Daniel

Well the issue for me is that I have one system working really well...no problems, and another system that isn't working.

For my AVs, I put them in domes when they are leaves and only have to water them every two weeks or so. They are VERY happy and I have no problems with this system. I changed a few of the pots to experiment with 5-1-1, I used Repti-bark. They molded really quickly, so I had to go back and re-pot all of them in 75% perlite, 25% miracle grow soil. They have no mold and look very happy. I've have never had mold issues before under domes.

As for doming, I have had huge success with completely closed domes and know lots of growers that do really well with domes, even repairing unhappy plants by putting them in domes. I'm not sure WHY it's so successful, but I've had more problems with the plants grown and raised outside of the domed trays than in. My guess is that I'm using less water. My water is horrible because I had the same conditions in my previous city and had NONE of these problems.

The reason I know that I have to change my system for my AVs out of domes is because they are staying very wet being wicked and also have fertilizer salts (although I haven't seen any more with the ones planted in bark and/or watered with distilled water, + allowed to dry out)

Even though I've solved the fertilizer salt problem, I now have to figure out if the yellowing leaves and slow growth has to do with the lack of drainage as Al explains it, or PH, or nutrient deficiencies, or both! lol

I'm already passed my budget on supplies, so I have to wait before I can get anything else, which means I'll be trying this mix that doesn't quite fit the standards of the "gritty mix". I'm still excited though because not having an organic medium means that I only have to worry about the nutrients and PH of the water...and I suppose the Perched Water Table possibly! but I have lots of tricks to get by that issue.

I'll be doing A LOT of experimenting and recording my results, maybe it will be of help to y'all! and maybe one day when I have an extra room to fit huge amounts of gritty mix supplies I'll be trying the real thing! :)

This post was edited by plantcrazed101 on Mon, Dec 9, 13 at 22:00

Please report back. The mix sounds similar to gritty mix and may work out for you. I did grow an AV in gritty mix for a few months until it was attacked by mealy bugs. The only problem with it in your set up might be that it is not designed to wick water. Good luck.

I did filter the mix so that all the particles were larger than 1/8 of an inch, and re-potted several plants, so now I just have to wait and see what happens!

Several are wicked, the wick is acrylic (I think) yarn. I know it's synthetic because I've used it for several months and it hasn't rotted or anything. A while back I started noticing the fertilizer salts and it seemed to coincided my switching from mason line (very thin, nylon) to this much much thicker wick that seems to pull up more water.

My hope is that with the wick pulling up more water and these pots that are 1-2 ounces, a few 3, it will be enough to make it self-watering but with the benefits of draining well.

I watered several plants and came back a few minutes later to find that the water really does drain all the way!! So I guess I'm doing something right :)