water?

What is the difference between ro/di water and distilled?

 

RO/DI water that comes from your own system and is tested by a TDS meter is probably the purest and best choice of water that you can use for your aquarium.

Distilled water is water that is heated to steam and is then collected and condensed. The idea being that nothing but water gets evaporated, and so this is pretty pure water. And it probably is pretty pure, unless it collects dissolved solids from the various pipes and containers that it is stored in.

Both RO/DI and distilled water are fine choices for a reef tank, though as I said above the RO/DI from your own tested system may be more pure. I once got an algae outbreak from using store-bought distilled water, that I later tested to find had 10ppm dissolved solids (we shoot for 0ppm with RO/DI).

 

bump

 

distilled water will have a low ph tho because its you know.... distilled so probably neutral around 7.0 as apposed to 8.3

 

They are virtually identical. The way it is filtered varies but the quality should be about the same with good RO/DI being slightly more pure.
You cannot accurately measure the pH of either one since theer are too few ions to measure. The pH is a moot point as both quickly take on the characteristics of whatever you add them to or add to them.

For a small system buying distilled may be cost effective but for larger systems the cost of purchasing water gets expensive and a RO/DI system is the way to go at less than a nickel a gallon of treated water on average.

 

The king has come. haha. Just kidding. AZ is very knowledgable(sp?) and helpful when it comes to RODI filtration and water systems.

 

OK my bad I guess I should have said what I wanted it for. I just ordered the two part dosing Cal-Alk-Mag from Brs and they say ro/di or distilled and want my choice to be the best. Thanks to all. I don't have ro/di so I will buy some distilled.