How to add some programming into Automatic Water Tank Level Controller

sorry i'm not in the mood of full presentation, and i dont have this ultrasonic sensor and never programmed it. i only can show you the example link, you should modify the code to suite your need, here https://arduino.cc/en/Tutorial/Ping if you have trouble modifying it, i'm sure it will be more trouble to me, if you ask me how, my advice only is just to learn programming. afaik, ultrasonic sensor is not suitable in high humid environment such as in a water tank. worst if it got splashed or submerged in the water.

non89,
Have you looked to see if PICAXE products available in Malaysia? They're cheap, easy to program, and I can help you. My Christmas tree watering controller is exactly what you want.

Here are some PICAXE vendors in you part of the world:
Japan Akizuki Denshi Tsusho Co. Ltd
Singapore Yuga Electronic Supplies
India Hobby2Go
Australia Wiltronics
Australia Altronics
Australia Robot Gear
New Zealand **broken link removed**
New Zealand South Island Components

Ken