RO/DI for Freshwater?

[ron101]

Originally Posted by reeferaddict

Ditto - remineralized is the way to go. What will happen over a period of time is that not only will the hardness/alk be all over the place, but the ionic balance of the water will become too dilute, actually causing osmotic shock to your animals... to use it once in a while for a 10% water change is fine for reducing nutrient levels and algae control, but prolonged use will eventually make your water uninhabitable... I did this once and wiped out a tank... sometimes we have to learn the hard way... *SIGH*

Remember don't confuse alkalinity with hardness. Measuring alkalinity can be a method for inferring hardness but they are not one in the same. Alkalinity is a measure of pOH (inverse of acidity). Water that has a high carbonate hardness (KH) tends to have a ph greater than 7 and good buffering capacity; as in it is considered alkaline not acidic. Pure/RO water has no carbonate hardness and thus no buffering capacity so pH can swing uncontrollably (both up and down).

Like Steve said even soft water fish like discus and South American cichlids will require some reminerilization to their water if RO is used. FYI the water in the GVRD is already quite soft and a little acidic; RO is probably overkill but if you already have access to it...

If your water source is hard then RO/DI will be the only reliable way to soften your water. Peat and acid products are quickly consumed by the carbonates and will leave a bunch of neutralized compounds in the water.