This is the most simplest diy auto top off water i did recently. Actually this not even can called a DIY project because its very simple to build.

I'm not using any pump, electric or what so ever that i have to buy :D.

Purpose:
- To replace evaporated water from aquarium

The material used :

• again my empty salt bucket (25kg)
• valve control (i take out from my previous DIY sulphur Denitrator)

Other thing need to consider

• run a test for leaking before plug to your aquarium
• since its a dripping based, find most suitable drip per second for your own need.

If you looking to a proper diy auto top off using floating pump, please refer to this thread at chuisui