It's been a while since I've been on this forum. I hope it's okay to post this pic.
Do you see the clear totes on the shelves? They approximately 12x14x15. I used to have most of my fabric in 18 gallon not see through totes like you are describing and I could never find what I wanted. Then I started to do a photographic index so I could "shop" my fabric on my computer. I took a picture of each fabric with a number tag (number written on scrap paper) sitting on top of the fabric. And then I had a word file organized by number that gave fabric description, quantity etc. So I could shop my stash either by pictures or by numbers. Eventually I was going to make a seperate list organized by types of fabric. I also wrote down what tote each fabric was in. While doing this I realized moving those heavy totes around in a cramped environment just wasn't working. So I decided to get the smaller totes and divide the entire stash by color. I do still plan to go back and do the photographic inventory at some point but for now fabric is sure a lot more accessible and organized. Good luck.
Edited to add.. After I looked at my post I noticed that some of the 18gal totes are in the pic so you can see the difference. Also this was a work in progress photo All the shelves are full, and there are more around to the side the entire length of another basement wall. I think I started with like 50! 18 gal totes