ok guys i got a response from DA to my email with same question as posted in my first post. here is their reply.
I'll give you a little information on the ReefKeeper system, and hopefully you can determine what specific combination of things you'll need to suit your purposes.
One of the primary advantages of the ReefKeeper system is that it is designed to be completely modular and expandable. You can start out with the most cost-effective $119.99 system, and add any additional Modules as needed. At its core, the ReefKeeper system is a head unit (like the RKE or RKL) and a PC4 power strip, providing 4 individually controllable, programmable outlets. Each PC4 is capable of handling 15A/1800w total, 8A on Channels 1 and 4, and 3A on Channels 2 and 3. In addition, we offer numerous Modules which provide anything from lunar simulation (the MLC), controllable dimming (ALC), switch inputs, pH, ORP, Temp and Salinity (SL1 and SL2). The NET Module will set up a webpage that is viewable from within your network (or externally with some additional setup) and can be configured to display graphs of your various parameters, as well as send text and email alerts. With the latest NET Module firmware, you are also able to change the Mode (On/Off/Auto) of any Output, as well as edit the Functions of any Channel. The ReefKeeper Lite has a 4 Module limit, while the ReefKeeper Elite is capable of adding up to 63 Modules, giving you almost limitless expansion to suit your needs.
For your system, you will have to determine how many outlets/Channels you will need to control and run everything, as well as deciding which (if any) modules you would like to add. Be advised that we also offer our PC1 and Expansion Socket Modules specifically to enable increased power handling, for higher current devices like chillers or large lighting systems.
I hope that all makes sense. If you have any additional questions or need clarification, please don't hesitate to ask. In addition, I suggest you check out our Support Forum, where you can find feedback and advice from current users of the product.
Thank you,
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Digital Aquatics Support Team