Oh forgot to mentiom a pro tip cause everyone knows how salinity probes tend to be worthless.... get a singlr inline probe holder for it. When it throws off pulse up your flow through it and it will clean it up. Ive got mine within 1 ppt of a fresh calibrated hanna. Been a while so might opt to recal the apex probe soon and maybe grt it even closer. But its really nice since hard plumbing and adding the cor-15 any time that probe goes awol i can just pulse the pump for a few seconds and the probe will reset... next step is to figure out how to automate that!