I am doing same. Been working on it for a couple months in my off hrs. Got quite a bit of the pieces and am starting to bring it all together into a "finished" version. I am currently mostly running on a Reef Angel with no problems except extensible and I hate coding things by hand! Node-Red is freakin awesome! I have Atlas Scientific EC and PH sensors online, Scheduled dosing using peristalic pumps, calibration, Relay banks, lights tied to sun position, and a number of other odds and ends. I am pushing to get off of the RA soon. I still need to build out a DEV environment and work through maintenance and source control before I switch.
<rant>
I am all in with open-source. The model I have seen with RA is good. Lots of folks want to buy parts off the shelf and extend others want to build from scratch. You "can" do both. They sell the soldered and prettied up ready-to-use boxes which cost money to build and maintain so them making some money on that is only fair.
</rant>
Next Steps?