Bottle tops in the bio filter

Shaunohara11

Not a question, more my experience. I.m just setting up an ibc 900l, 2 filters of 300l total, a small nft and 2 dwb of 300l l each.
Reading about the filters, i read somewhere that the second filter, in order to increase the surface area for the bacteria, you could use plastic bottletops. I had everyone collecting their tops.
I have connected the tanks with 50mm pvc, but forgot to put mesh over the outpipe from the second filter.
The tops were sucked into the pipe and parcially blocked it, causing the water to backup and overflow.