I drilled large holes in a large dia pipe was left with a gallon of compresed pvc ribbon I,ve cut 1/2" PVC into wafers.Stole my kids bristle block set he never liked anyway.Used a bag of lava rock for the last 5 yrs love to attach plants to the rocks (in the tank)
For your tanks filters fill them with your diced straws.Also consider useing filter floss in those instead.