deionized vs distilled water?

[nkresho]

How about RO (reverse osmosis) water. Can get it from my local pet shop to be used in fish tanks where you don't want any hardness/softness in your water. Its pretty cheap aswell, £2.50 for 25 litres.

I have always used r/o in my loop.

My r/o filter brings my city tap water from about 400ppm down to about 8ppm. I kept saltwater fish and corals for years and have always purified my own water. It's as good/pure as distilled IMO. Just make sure to ask the fish store to tell you how clean it is. If they need to replace their membrane it won't be all that clean as compared to regular tap (might even be worse as it releases impurities back into the water). They would need a tds (total dissolved solids) meter to check it, it measures in ppm (parts per millionth). Lower is better.

hmm i wonder if natural glaciar water would work.... i can get a gallon of that, my dad is going out to iceland this weekend... how would that go in a system? like straight from glaciar, pure water..

Nope, that has way more minerals in it than other types of water. You would most likely get visible deposits on the insides of your blocks/pump/etc.