Hey Sunmark14,
I'd start with gathering all the required hardware to monitor. The big question is 'what' you want to monitor/control.
The hardware i used came from Ebay except for one part. Thats the Phidgets 1130 pH/ORP module. If your from the US, getting one shouldn't be a problem. If you live in Europe, you'll have to look a bit harder 
These are the parts i used...
Arduino Mega 2560
Aquarium Peristaltic Dosing Pump head
pH Electrode Probe
Phigets 1130
4 Channels 5V Relay Module for Arduino
Pressure Solar Water Heater Dedicated 12V Solenoid Valve
DHT11 Temperature & Humidity Sensor Module
20PCS Photoresistor GL5539 LDR Photo Resistors Light-Dependen?t
3.2" TFT LCD Shield + Touch Screen TF SD Reader
2x Gray Duckbill Side Water Level Sensor Liquid Float Switch
SD Card Module Slot Socket Reader For Arduino
14pcs 2X40Pin Double Row 2.54 breakaway Male header
I2C RTC DS1307 AT24C32 Real Time Clock Module
5 PCS Bread Board Prototype proto Board 10*20cm
DC 9V/1A Power Supply For Arduino
After you acquired the parts you need, check out the code i wrote. Almost everything is made up in blocks, so if you don't need the LCD...you can leave out the graphical and touch functions. And the logical part will still work. Tip also remove the call to those functions in the void setup() and void loop().
Have fun and remember...If you improve on this design please post it back here