I will tell you my experience with 5-1-1 mix, which I changed for a 6-1 mix (I will explain it). Until one year now, I used a commercial mix of compost and peat for citrus containers, with very good results in the short term (several months), but with further problems due to organic matter decomposition with lake of air and and the resulting problems. Then, I decided to move to 5-1-1 mix, but it is difficult to find pine bark of 3/8" size. Repti bark and Orchid mixes are very expensive. I buy 1 inch size bark mulch in 6 gallon bags at a very good price. Later, using a pruning woods chopper, I triturate the bark mulches and screen out pieces bigger than 3/8" size. What I get is a family of bark particles from fines to 3/8" size. I tested by myself several mixes in a container of 25 Oz volume and 6 inch high and I got the following results: 5-1-1 mix (chopped and 3/8" screened bark+perlite+peat): Total pore volume: 300 ml Aeration pore volume: 130 ml Total porosity: 40 % Aeration porosity: 17.3 % Water-holding porosity: 22.7 % 6-1 mix (chopped and 3/8" screened bark+perlite): Total pore volume: 400 ml Aeration pore volume: 250 ml Total porosity: 53.3 % Aeration porosity: 33.3 % Water-holding porosity: 20 % As you can see, I got better results, by far, from 6-1 mix, without peat. I decided to try without peat, following a Josh (Greenman28) advice in an old post. He said that sometimes he didn't use peat in 5-1-1 mix with good results. Peat decomposes faster than bark, and you know that decomposed particles penalises aeration. Well, after one year of use of 6-1 mix, I bare rooted the past week a healthy Tango mandarin grafted on Poncirus trifoliata in a 12 gal container, for planting in ground, and I can tell you that the mix was in a very similar condition to the original, and I don't remember so well developed and healthy roots in a container citrus plant. I am very satisfied with this mix. Just one additional care with it, you have to monitor more closely the fertilization, because minerals leach out easier than in a traditional peat mix. In any case, it remains for an acceptable time. And, coming back to your question, I don't remove fines. If you removed fines, in my opinion, it would be imperative to use peat.

My recollection is that you DO NOT want composted material. I would go with the 12 mm medium pine bark fines. Per Al, his gritty mix bark recipe should include 1/8" to 3/8" pieces. After sifting them out, sift again to remove the smaller particles. It looks like the 6 mm material has a lot of very fine bark and your loss would be much higher than the 12 mm bark. It's helpful if you can actually see the material as pictures can be deceiving and each lot could be different. Keep in mind that I'm no expert but I've sifted a lot of bark (different brands, names, etc.). Good luck!

I actually prefer the nuggets because its all bark and not yellow wood or garbage. Yes they are too big for potting mix as is but I chop them up in a blender (don't tell my wife I do it when she's not here). Just cover the mulch with water and pulse it a few times. Then I pour the mixture through a pond basket to wash out the fines that are too fine. I make a big batch and put them in a bucket with blood meal and fish emulsion (yes it stinks for a day or two) then a week or two later rinse and its ready to be a potting mix component Wanton i think 5 1 1 is a recipe like 5 of these one of those and one of those.

Okay, thanks guys. I figured I wasn’t able to use it but wanted to make sure I wasn’t being overly cautious. Thanks again!