The stuff- chemical- released from cinder brix is fly ash. Its possible to paint or line inside the bricks if its a concern. Watch your calcium levels in a raised bed- those cinder brix contribute zero.
Love the mushroom compost. Cow compost too- but if you buy by the bulk from Monterrey mushroom, that chicken poo and straw can build huge plants and do more growing than producing. Gardner Bob is right about fire ants, but its an ongoing fight as they find hi ground in every rain. We also have moles- the bottom of my bed is edged with metal fabric and the bricks set on top of the fabric.
Down here the only stuff I can bring in as bulk disintegrates to fine silt sand. Since I originally did not line the beds with plastic, watering draws the tree roots.
