I keep seeing 2 cups for an 18 gal swc but does that mean I only need 3/4 cup in each? That is a very good question and I don't know the answer. I don't use granular fert on or in the mix in SWC precisely because I don't know how to figure how much is actually being delivered to the plants. At the end of a season when using a granular strip of fertilizer there is an awful lot left over that appears to be intact. Normal procedure is to scoop it out before the next season. While 2 cups of synthetic fert per 15(or in your case 18) gallons of potting mix seems to be the norm (established by EarthBox grow out trials), I really don't know if that means you can reduce that to a per gallon of soil amount. This is one of the reasons I don't use granular fert in SWC, but instead use water soluble ferts in the reservoir. It gives me more control and I can adjust more easily if things appear to not be working well. This actually sounds better than regular MG but would the micronutrients stay in the soiless mix after a month or two or three? In a traditional top watered container with a drainage hole that would be a fair question, but in a SWC which is a somewhat 'closed' system where would the micros go other than into the plant or into the reservoir if they are water soluble? Some nutrients such as nitrogen are subject to volitization, but as far as I know this isn't a factor with the micros. If you flush your SWC during the growing season you can expect the water soluble portion to go bye-bye, but otherwise they pretty much have to stick around. I still think the limiting factor in your case is going to be lack of water and possibly nutrients with 2 indet tomatos in a 5 gallon bucket, SWC or not. On the other hand you indicated you have the time to tend to the plants so you may well make it work. I certainly don't wish to discourage your attempt. You are going to have far more control with a water soluble fert in the reservoir than you will a granular fert on the soil surface though. I would recommend you look into Foliage Pro 9-3-6 and Pro-Tekt 0-0-3 for a complete nutrient souce that is 100% water soluble for the reservoir. By diluting both to the same degree you end up with a 9-3-9 fertilizer which is a 3-1-3 ratio which is what tomatos actually use throughout their entire life cycle. All you need to do is some trial and error with your plants at various growth stages to determine the optimal dilution rate.

Sphagnum Peat Moss is the magic that makes SWC work, I have grown in it straight before but tomatoes are so vigorous they would probably grow in anything. I had so much trouble finding a potting mix locally that had the 70% peat as suggested by EarthBox that I ended up adding half Peat to purchased potting mix. Recently, my local Home Depot began stocking Promix HP which works great.

Thanks for your replies and all your help Raybo. I'm thinking since my aeration bench is already cut out for a 6" dia hole I'll probably put a patch over that hole and cut a 3" hole into the patch. I would think that the size of the basket in the reservoir would not matter since only the wick size would still be 3". Last summer my SWC mix stayed very wet and all of my tomato plants showed signs of to much water. But I was not mixing anything into my Sta-Green potting mix. I also reused some of the previous years mix. I used only 1 cup of Lime, 1 cup of Epson's salt and no fertilizer in the top of my mix. Yet I still produced a ton of tomatoes. Is my thinking correct? Joe

Raybo...another scale question for you. I believe that your instructions call for 3/16 inch drill bit for the holes in the aeration bench. In scaling my container down to 22 gallons, should the holes still be drilled with a 3/16 inch bit? I started with a 1/8 inch bit, but it seems awful small, even for a smaller container. (BTW-I ended up using a sour cream container for the wicking basket, that is approximately 4" deep and 5 7/8" in diameter.) My 'Tainer is already coming along nicely, though!! I have to admit that I was a bit intimidated, yet eager to try building one on my own, but intimidated enough to put it off for a while. (was that proper grammar?) Now that I am progressing with it, I am anxious to build more! (hello...Corn'Tainer?!?) Thank you for sharing your plans and expertise with everyone. :o) RTG