Sand Bed Clumping

[Andy]

Hello

Over the last several months, I have noticed that my sand bed is clumping (cementing) in places. I'm using CaribSea Select aragonite sand. My alkalinity is at 9 dKH (3.3 meq/l) and calcium is between 400 and 450 ppm. I use a calcium reactor and kalkreactor to keep calcium and alkalinity at their current levels. pH ranges from 8.15 to 8.3 daily. I usually don't touch the sand bed. I have 3 cucumbers that spend most of their time in the sand. No other sand sifters. Does anyone have any suggestions as to why the clumping is occurring and what I might do to prevent it.

Any ideas.

Thanks,

Andy