coir is OK if you can get it with a low salt content. The professional mixes available from landscape yards are using it and those have worked for me. My own experience with a compressed brick was not good.

It is also instructive to me that @tapla (mid-Michigan, USDA z5b-6a) chose to use peat moss - and neutralize it with dolomite lime - in his 5-1-1 mix. That speaks highly to the idea that a little peat moss goes a long way in improving moisture retention of container soil.

i was advised to leach my brick, i dont know if it had salinity issues. i love coir in lieu of endangered peat bogs.

"i love coir in lieu of endangered peat bogs."

The US peat moss supply comes almost exclusively from Canadian sources (the exception is reed peat, produced in very limited quantities in the US and without the same characteristics of sphagnum peat moss). And Canadian peat bogs are in NO danger!! Less than two tenths of one percent (>.02%) of Canadian peat bogs are farmed for peat and even those are harvested sustainably with replanting happening just like any other farmed crop.

Much ado about nothing!!