Clogged PVC problem

[tang daddy]

I use to dose the big 3 in my sump, after 8-10 months I noticed the return pump have problems starting after it stopped so I took it out and to my amazement was a cement blockit was so calcified that even a chisel would bounce off. So in it went into a bucket of vinegar. I think most reefers overlook this problem and return pumps should be cleaned frequently like every 6 months.