Why do saltwater tanks need RO water, and why freshwtaer tanks don't

Why is it that freshwater aquariums are perfectly fine without using RO water, and by using tap water, but saltwater aquarists say you MUST use RO water for marine tanks? (assuming there are no corals). Pls reply, i have never been able to get a straight answer....

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Comment by LED on June 27, 2014 at 1:51pm

In a sw FOWLR tank youll have more issues with certain types of algae that feed off the nutrients in tapwater.  So by removing the nutrients via RO process you will reduce the chances of getting bubble algae, hair algae, cyano, diatom.  blah blah blah  algae.    

Yes you can use tap water but you never know what nutrient levels you're getting, what pollutants your getting, and it always a gamble.  Yes its faster but remember youll have to reduce all those nutrients with chemicals.  After a half year or one year youll have spent more in chemicals than on a RO unit.  

Reason FW dont always need RO water is that many fauna are not as picky, lighting for non planted tanks is far lower and doesnt promote algae growth.  If one does have a planted tank, fw plants take up certain nutrients that sw coral and plants dont use as readily.  Now there are exceptions.  Some plants and fauna need RO water to thrive, breed, blah blah blah and you can find examples on google.  There are always reasons to use purer water than our taps.

Hope something I said clears some questions.


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