Mary,
Only the soil packed around the edges and up to the top of the colander is immersed and in constant contact with the water...it's not that much compared to the remainder of the mix in the bucket...
I refreshed 6 eBuckets for bell pepper plantout this weekend, and decided to stick with straws for now, since out of about 35 eBuckets, I've only had issues with 2 buckets of anaerobic potting mix. And, I think it was more a case of me running into the straw and bending it than any soil actually collapsing them closed. I haven't encountered a mashed or collapsed straw yet.
When I construct, I take care to pack the potting mix under the straw tightly as I can get my finger in there. Then, I pack it on top of the straw tightly ensuring good support for the straw.
My next insurance is to use the big MALT straws from McD's. Finally, in cases of extreme rare doubt, I have taken to double-walling the straws. They're not gonna collapse, ever...
So, the real consideration is "exactly how much of an airspace do we need between the soilbed and the reservoir? I might just pick up a length of that tubing to outfit one more bell pepper eBucket as a comparison, to see if there's any observable difference in growth. The only varying factor would be the airspace in the eBuckets.
Linda
