So a recent icp test showed high aluminum.
MarinePureBio Blocks are known to leach aluminum.
I have (had) five of the 8x8x4 blocks in the sump.
I didn't know this before putting them into my system.
I've lost quite a few corals over the two years the tank has been up.
Always with great growth for many months to over a year, be it size or in additional polyps, and then crashing within a matter of days to two weeks. And always in the order they were placed into the system. I wish there was somewhere I could send some before a complete crash to verify it is aluminum poisoning, but my guess is they reach a saturation point and then die.
So yesterday I removed four of the five blocks (I'll remove the fifth after testing for a week to make sure I don't get any spikes) and replaced them with 8 liters of the SeaChem Matrix.
Fun exercise as some of them float until the air is pushed out of the pores. One got by me undetected until it got sucked into the return pump. Thank goodness for auto shutoff when the impeller gets jammed.
Thank goodness I soft piped it to the pvc and was able to work on clearing it without having to disconnect it. (time was an issue as we were meeting mom and dad for dinner.)
Got the pump cleared and back on. Dumped in a bottle of bacteria to fast start the Matrix.
No fish floating so it looks like everything survived the night. Testing later this afternoon when the lights pop on.
Something at some point was tunneling into the block.
Other people have complained about the blocks crumbling. That was never an issue for me. I was concerned, after reading those reviews, that they would come apart when I removed them.