OK, I got enough coarse sand together (on consultation of my esteemed missus, she confirmed which fraction looked best) and the thirteen seeds that sprouted out of nineteen which had swelled have now been planted in the 65:25:5 sanderlite:coir mix. Photo story to follow.
EDIT: I've just realised I got the perlite and coir amounts mixed up
And to think, I not only double-checked, but also thought "that doesn't seem like much coir" I guess I'm too accustomed to cactus gardening and high-mineral substrates and just shrugged it off, thinking acacias must prefer low-organic compost, especially since my first acacia grow failed due to using compost with way too much organic content.
coarse river sand, peat moss/coco coir and perlite at a ratio of 65:25:5
Well, so much for attention to detail - do you think this foolish but easily-resolved error should be dealt with as soon as possible, or should I now wait until the seedlings have strengthened some more? Because right now it would still be very easy to prick them back out of what is essentially sand, and simply mix in an appropriate amount of coir to - hopefully - make things a little more hospitable for them. The current mix is so loose that one of the seedlings had pushed itself out of the sand:I’m impressed you went to such effort to sift the fine sand out.. attention to fine details like that really will make a difference in the seedling’s early development
and I've subsequently re-set it into its hole:
I'm concerned that if I leave them longer, this may stunt their growth, but then again, coir contains bugger all nutrients anyhow and the low organic content may help prevent mould, so I dunno...
To reiterate, the ratios ended up being 65:5:25 coarse sand/coir/perlite.
I can either sort it out first thing or wait for the plants to grow. Which option is best - or is there some super-genius level solution that I've overlooked (like Scott's Osmocote or whatever)?