Got thrown a curveball today. Project temporarily derailed due to material issues.
One problem solved and another popped up. The intake stems on the powerheads I was able to secure with washers. However an issue with the containers happened when I shook them loose of media dust that collected on the bottom. Underneath the base was one of those "Proposition 65" warnings about cancer causing materials. It only mentioned silica, but since the product is from China there's a good chance the glaze contains lead. So I'm not taking the risk. For those of you not aware glazed ceramic products in China often contain lead.
So the vases are OUT as filter boxes. I've already repurposed them as candle holders in my living room. Making chicken salad out of chicken **** like they say.
Funny how sometimes fate works. I was going to show the final assembly today before testing. So I'll be getting new containers. Will post updates.