RO water for freshwater tanks

locoyo386 · June 17th, 2009

Hi there,

I heard that RO water is not goog to use in freshwater fish tanks.

Is this correct?

If so, why?

jdhef · June 17th, 2009

Since no one answered yet, I'll take a stab at an answer, but I don't know if this is correct or not.

I don't think that RO water is bad, but I think that RO water is missing all of the trace elements that regular water contains. I think when using RO water, you are supposed to add trace elements (you can buy them in a bottle).

Also, I think there could be some pH issues, since all of the buffers contained in the water have probably been stripped out.

Of course if I've given out any wrong or incomplete info, I welcome any and all corrections!

lew2000 · June 17th, 2009

Quote:

Originally Posted by jdhef

Since no one answered yet, I'll take a stab at an answer, but I don't know if this is correct or not.

I don't think that RO water is bad, but I think that RO water is missing all of the trace elements that regular water contains. I think when using RO water, you are supposed to add trace elements (you can buy them in a bottle).

Also, I think there could be some ph issues, since all of the buffers contained in the water have probably been stripped out.

Of course if I've given out any wrong or incomplete info, I welcome any and all corrections!

Jdhef is right. RO water does not have any buffers: KH, which means that you can have pH swing once you have fish and the nitrification process going. RO water is missing virtually all/any trace elements, these need to be replaced. The other aspect of RO systems, is that to remove chloramine (most municiple water systems use now) you need to make sure that the RO system you use has a filteration for this.

Most people use RO for Saltwater tanks - becuase the salt mix has all of the elements and KH properties required.

locoyo386 · June 17th, 2009

Hi there,
Thanks for the help. I guess I am better off using tap water with water conditioner or letting it sit for a day or two to let the water vent.

jdhef · June 18th, 2009

Chloramines do not disapate by letting the water sit, like chlorine does. So you should always use a water conditioner with city tap water.

Nate McFin · June 18th, 2009

It can be beneficial to do this for some circumstances. For instance if your tap has a low Kh and has large Ph swings. Low Kh can be a bugger in planted tanks as the small buffer you have can easily be used up as nutients by the plants leaving you a very low Ph quickly. As said you will have to buffer the water yourself but you are able to set the Ph, GH, and KH exactly where you want it for your fish and plants. Not an easy process and not recommended unless you have to.

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