# Reverse Osmosis - DI questions



## t2000kw (Jul 29, 2006)

I am thinking of buying a reverse osmosis unit to allow me to have softer water for some of my fish, including some discus a friend will be giving me soon. (I would consider buying one used from a club member if someone needed more output and theirs was still servicable.)

The discus are actually acclimated to our Chillicothe water other than having the water passed through a carbon block filter before adding to the tanks.

We do use some for adding to the angelfish tank, and it costs about 40 cents per gallon at Wal mart. Not bad, but not convenient to get it, either.

Here is a unit I am looking at on ebay:

if the link doesn't work or you have to copy/paste it into your browser, it might be easier to just do a search on ebay for the item number:

Ebay item number: 120063301574

eBay: WaterGeneral RO6100+DI 2 OUTPUT REVERSE OSMOSIS RO + DI (item 120063301574 end time Dec-16-06 19:41:56 PST)

Anyway, I am mostly concerned about the DI filtration. I partly grasp the concept of deionization but do I need it, is it safe for freshwater fish, or will it add some salts to the water? I have read that some DI filters do add salt to the water and that can be detrimental to discus.

Also, is it possible to add another pressure tank to store 10 or 20 gallons more water to have available on demand? I'm thinking of those ones used for well water to even out the pressure changes and that keeps the pump from cycling off and on continuously.

Any other helpful thoughts you might have are welcomed. I can ask the seller other questions I have (like, do these use "standard" size filters, etc.).


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## MatPat (Mar 22, 2004)

As far as I know the DI filters on RO/DI units do not add any salt. They are not like water softeners that use Sodium/Potassium chloride to soften water. 

That said, I have the same unit in your link (without the 3g under sink pressurized container) and it has been running for nearly 2 years now without any filter changes. I am still getting water with a TDS of about 2ppm (0ppm is pure) so I could probably stand to flush the unit  I didn't see the need for the under sink unit since I did not plan on drinking the water.

If you want to use a storage container for the water, do not use a pressurized one like the RO filter in the link has. The pressurized storage containers are only for use when you put the container under a sink for drinking water. A 30g or larger trashcan will work much better. You can install a simple float valve to turn off the RO unit also. Much better then the pressurized container. However, you would probably want an additional pump to get the water from the storage container to your tanks so take the additional price of a pump into consideration  With a trashcan storage type container, you can also put a heater in there so there are no temp shocks to the Discus.


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## t2000kw (Jul 29, 2006)

How many gallons per week, month, or year do you think you pull through that filter?


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## MatPat (Mar 22, 2004)

I honestly have no idea how many gallons of water I have processed with the RO/DI unit. It sat idle for about 6 months now that I think about it. As a *guesstimate* I make maybe 40-50 gallons a week for topoffs and water changes in one 75g tank.


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## t2000kw (Jul 29, 2006)

Does this seem to be a good price? (see previous post for ebay link)

Also, do you use a special filter to take out ammonia (after the carbon block filter which would leave some ammonia after removing chlorine from chloramine, right?)?

Check out the "blaster" filter here (you'll need to scroll down a bit to read about it):

WATER PURIFICATION FILTERS

I suppose if ammonia is an issue I could just use amquel, but the part that splits the chlorine molecule off and detoxifies it (relases it into the air) would be wasted.


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## t2000kw (Jul 29, 2006)

I bought the filter today and got a permeate pump to cut down the wastewater. I hav eto pay for the water AND for sewage treatment even for water that is rather clean, so the less wasted, the better.

Does anyone treat their RO output for ammonia or should it be OK?


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## MatPat (Mar 22, 2004)

t2000kw said:


> I bought the filter today and got a permeate pump to cut down the wastewater. I hav eto pay for the water AND for sewage treatment even for water that is rather clean, so the less wasted, the better.
> 
> Does anyone treat their RO output for ammonia or should it be OK?


I don't think you need the permeate pump unless you are pumping water into a pressurized container but maybe it will help.

I also don't think you will need to treat your RO water for anything. It should be pure or very close to it...that is the point of an RO unit. My RO unit produces water with a TDS of zero and I backflush it when the TDS rises into the 5-10 ppm range. Even at 10ppm TDS that is very soft, pure water. Our hobbyist test kits won't register any GH, KH or anything else in the RO water. My Tap is in the 200-250ppm TDS range depending on the time of year for an example of how many contaminants the RO unit removes from my water.


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