as I was working I was thinking about this, on how people would plug in a probe etc to monitor/control their PH, co2, salinity, temp etc.
pH is usually with a standard BNC
CO2 probes are expensive; do you plan to purchase one?
Salinity is not really needed in a planted aquarium. But they are also BNC.
Temperature is just with the DS18B20 from Dallas. You can put it into a waterproof container and it will work fine.
my other concern was how small the screen is I was hoping to have a screen at least 6x6 inches so it could be easily seen from a distance. Maybe something we could look into?
6x6 inches is quite large; I assume you want it to be touch screen too? It will be quite expensive.
To get an idea, the iPad measures 9 x 7 inches.
Dark PM me to please I have an idea I want to run by you that is kinda off topic.
You could PM me too, you know...