Question for all of you that have or SELL controller's

[The Grizz]

Ok so I think I have it figured with some inlightenment from Kien. Here is what I might look into.

Neptune Systems Apex Lite Controller Package:

-Package includes: Apex Lite Base Unit, Apex Display Module, Temperature Probe, and Energy Bar 8 Module.

And add on:
- Conductivity Probe
- pH Probe - Lab Grade
- ORP Probe - Lab Grade

Any other suggestion for add-ons