Look up the toxins leached from cement and cinder blocks. The advice is to line beds to prevent soil coming into contact with cement, cinder blocks, concrete because most of it now contains fly ash and/or bottom ash from coal fired electricity plants.
Although fly ash is more stable when mixed with cement than when it is loose, it still leaches heavy metals in small amounts. A literature review could not recommend concrete for water tanks.
It is quite gutting, really, as my budding permaculture garden is in a back garden full of concrete.
https://beauregardparishcountrylife.wordpress.com/2014/07/02/gardening-note-toxins-in-concrete-blocks-and-concrete/amp/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968176/
