For the inert component, I am unable to find granite chips. I thought about using similar sized inert aquarium gravel since it does not affect water chemistry. Would this be ok? Yes, but size is an important consideration. Try to keep the size as close to 2.5-3.5mm as possible. If these are the larger clay balls that are greater than 5-6mm in size, I'd look for something else. Do you have Seramis available there? Calcined DE? The Seramis would be structurally stable, but you'd need to test the calcined DE by way of a freeze/thaw cycle to test stability - not that I'd expect it to freeze there, but it's a reliable and quick way to test for stability. At least 1 other ingredient that holds water internally should be a part of your medium.

Should I just use a 1:1:1 LECA, Gravel, Bark mix and water more often or just use a 100% LECA substrate? On its face, the gritty mix seems to be something I threw together with no consideration other than sharp drainage, but the deeper you look the more you realize there's a reason for everything. That's not to mean there are no substitutes - there are. It's just what's easily available to me and offers flexibility. There is little sense in going to the extra effort and expense of making a soil if you're unable to build into it the advantages that are available to you. I honestly think it's better to be patient until you find ingredients you are reasonably sure will no a great job, and not those you suspect might only be marginally acceptable. I think many growers read about soils like the 5:1:1 or gritty mix but don't fully understand the concept from which they were born. They use what they can find, even if inappropriate, and are often disappointed for any of a number of reasons, which leaves a bad taste that has them swearing off of "that soil nonsense" forever ..... and out goes the baby with the bathwater. I've found that the single largest step forward a container gardener is ever likely to make, is getting the soil right. It makes watering and fertilizing monkey easy.

Which leads me to question, what are the disadvantages of a 100% bark mix compared to a 1:1:1, since the water retentive and structural attributes are similar? What am I missing? This is one of those things I was thinking about when I mentioned the deeper you look, the more you realize how much thought went into the gritty mix's make-up. The gritty mix is formulated to retain its structural integrity over years of service. If you make a soil with a large organic fraction, the soil will collapse over time and there will be enough sludge at the bottom of the pot to generate unhealthy root conditions, which include fungal infections and unwanted soil gases, like methane and CO2. If you limit the organic fraction of the medium to no more than 1/3 of the mix by volume, no matter how much breakdown of the bark occurs, the remaining 2/3 inorganic fraction will guarantee the soil will not collapse - even after 10 years. IOW, if you depend on the bark for your soil's structure, in time you'll have issues. If you depend on the larger volume of inorganic material to provide the soil's structure, you won't have those issues.

Al

Hi Al, I have managed to build my first gritty mix using fir bark, aquarium gravel and pumice - and repotted my grape vine into the mix.

How long after repotting should I begin to fertilize?