Use the OAT Red or Orange Coolant, it has a higher boiling point and has a longer life. More efficient. Main ingredient is Diethylene Glycol. More popular in tropical countries. The Green coolant (Ethylene Glycol) has a very low freezing point. You don't need that because you don't have winter in your place, right?
Don't use water, Water boils at 100 degrees celsius, turns to steam, not efficient...
Rust also....