But I'm willing to learn how to use an mini pc to control my aquarium,
Things I would like to control are,
Power heads,
Pumps,
Lights,
Water sensors,
Temperature probes,
Ph of water,
Salinity,
An R O unit,
Speakers,
Hdmi touchscreen monitor,
To move cabinet doors
Feeding pump,
Possibly a few more things as well.
I can find the time to program, design, build and learn how all this will come together.
What I would like is my samsung S4 to communicate with the controller, I could also do a web page and get my own hosting server going too with remote control of the controller,
I would like an Android platform as it'll make my life easier getting my mobile to communicate (I think)
So can anyone point me in the right direction of where to start?
That's an ambitious first project. It sounds like a lot of I/O too, so you'll probably outgrow an Uno by the end of it, but I suggest you start with one - cheaper to replace if you have any accidents.
I'd suggest you pick one of your requirements - temperature probes sound good and get it working to the point where you can display the temp on the serial monitor in the IDE, then do another stand alone. By the time you've done a few, you'll have a better appreciation of the level of difficulty involved in doing the whole thing, but you can build a subset of the whole thing that actually does something and work towards your all singing all dancing version.
You can use this driver available here : GitHub - ksksue/FTDriver: Android 3.x USB Host Serial Driver
include the FTDriver.java in your android project; instantiate it and you can use read and write methods defined in there to communicate with arduino