Should I use RO/DI?

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Miller2112

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Nov 2, 2020
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I did a couple mixes last night. I did 1:1 and PH was still 7.8 I then did 2:1 (Tap:RO/DI) and Ph again was still 7.8

I'm thinking I'm just going to use tap water since its cheaper and use dechlorinater and PH down to lower the PH. Any major flaws in this approach?
Oh and by the way thanks for the help I definitely appreciate it.
 
Apr 2, 2002
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Something is not right. Pure ro/di should test as acid. It should not be anywhere near 7.8. Moreover, the ro/di has 0 KH. Is it possible that your test kits are old? When I mix my 7.0 tap with in an 11:9 ratio (ro/di to tap) I hit petty close to 8.0. However, My KH is in the 3 dg range.

Did you test the KH in the tap and then in the mixes? Also, did you make sure to stir up the mix before testing?

Here are a few quotes from the FINS site on basic water chemistry which should help:

Note: GH, KH and pH form the Bermuda's Triangle of water chemistry. Although the three properties are distinct, they all interact with each other to varying degrees, making it difficult to adjust one without impacting the other. That is one reason why beginning aquarists are advised NOT to tamper with these parameters unless absolutely necessary. As an example, ``hard'' water frequently often comes from limestone aquifers. Limestone contains calcium carbonate, which when dissolved in water increases both the GH (from calcium) and KH (from carbonate) components. Increasing the KH component also usually increases pH as well. Conceptually, the KH acts as a ``sponge'' absorbing the acid present in the water, raising the water's pH.
Raising and Lowering pH
One can raise or lower pH by adding chemicals. Because of buffering, however, the process is difficult to get right. Increasing or decreasing the pH (in a stable way) actually involves changing the KH. The most common approach is to add a buffer (in the previous section) whose equilibrium holds the pH at the desired value.

Muriatic (hydrochloric) acid can be used to reduce pH. Note that the exact quantity needed depends on the water's buffering capacity. In effect, you add enough acid to use up all the buffering capacity. Once this has been done, decreasing the pH is easy. However, it should be noted that the resultant lower-pH water has much less KH buffering than it did before, making it more susceptible to pH swings when (for instance) nitrate levels rise. Warning: It goes without saying that acids are VERY dangerous! Do not use this approach unless you know what you are doing, and you should treat the water BEFORE adding it to the aquarium.

Products such as ``pH-Down'' are often based on a phosphoric acid buffer. Phosphoric acid tends to keep the pH at roughly 6.5, depending on how much you use. Unfortunately, use of phosphoric acid has the BIG side effect of raising the phosphate level in your tank, stimulating algae growth. It is difficult to control algae growth in a tank with elevated phosphate levels. The only advantage over hydrochloric acid is that pH will be somewhat better buffered at its lower value.

One safe way to lower pH WITHOUT adjusting KH is to bubble CO2 (carbon dioxide) through the tank. The CO2 dissolves in water, and some of it forms carbonic acid. The formation of acid lowers the pH. Of course, in order for this approach to be practical, a steady source of CO2 bubbles (e.g. a CO2 tank) is needed to hold the pH in place. As soon as the CO2 is gone, the pH bounces back to its previous value. The high cost of a CO2 injection system precludes its use as a pH lowering technique in most aquariums (though see the PLANT FAQ for inexpensive do-it-yourself alternatives). CO2 injection systems are highly popular in heavily-planted tanks, because the additional CO2 stimulates plant growth.
Softening Your Water (i.e., lowering GH)
Some fish (e.g., discus, cardinal tetras, etc.) prefer soft water. Although they can survive in harder water, they are unlikely to breed in it. Thus, you may feel compelled to soften your water despite the hassle involved in doing so.
Typical home water softeners soften water using a technique known as ``ion exchange''. That is, they remove calcium and magnesium ions by replacing them with sodium ions. Although this does technically make water softer, most fish won't notice the difference. That is, fish that prefer soft water don't like sodium either, and for them such water softeners don't help at all. Thus, home water softeners are not an appropriate way to soften water for aquarium use.

Fish stores also market ``water softening pillows''. They use the same ion-exchange principle. One ``recharges'' the pillow by soaking it in a salt water solution, then places it in the tank where the sodium ions are released into the water and replaced by calcium and magnesium ions. After a few hours or days, the pillow (along with the calcium and magnesium) are removed, and the pillow recharged. The pillows sold in stores are too small to work well in practice, and shouldn't be used for the same reason cited above.

Peat moss softens water and reduces its hardness (GH). The most effective way to soften water via peat is to aerate water for 1-2 weeks in a bucket containing peat moss. For example, get a (plastic) bucket of the appropriate size. Then, get a large quantity of peat (a gallon or more), boil it (so that it sinks), stuff it in a pillow case, and place it in the water bucket. Use an air pump to aerate it. In 1-2 weeks, the water will be softer and more acidic. Use this aged water when making partial water changes on your tank.

Peat can be bought at pet shops, but it is expensive. It is much more cost-effective to buy it in bulk at a local gardening shop. Read labels carefully! You don't want to use peat containing fertilizers or other additives.

Although some folks place peat in the filters of their tanks, the technique has a number of drawbacks. First, peat clogs easily, so adding peat isn't always effective. Second, peat can be messy and may cloud the water in your tank. Third, the exact quantity of peat needed to effectively soften your water is difficult to estimate. Using the wrong amount results in the wrong water chemistry. Finally, when doing water changes, your tank's chemistry changes when new water is added (it has the wrong properties). Over the next few days, the chemistry changes as the peat takes effect. Using aged water helps ensure that the chemistry of your tank doesn't fluctuate while doing water changes.

Hard water can also be softened by diluting it with distilled water or R/O water. R/O (reverse-osmosis) water is purified water made by a R/O unit. Unfortunately, R/O units are too expensive ($100-$500) for most hobbyists. R/O water can also be purchased at some fish stores, but for most folks the expense and hassle are not worth it. The same applies to distilled water purchased at grocery stores.
http://fins.actwin.com/aquariafaq.html Click Your First Aquarium or skip the home page and go here: Practical Freshwater Chemistry
 

Miller2112

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Nov 2, 2020
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Something is not right. Pure ro/di should test as acid. It should not be anywhere near 7.8. Moreover, the ro/di has 0 KH. Is it possible that your test kits are old? When I mix my 7.0 tap with in an 11:9 ratio (ro/di to tap) I hit petty close to 8.0. However, My KH is in the 3 dg range.

Did you test the KH in the tap and then in the mixes? Also, did you make sure to stir up the mix before testing?

Here are a few quotes from the FINS site on basic water chemistry which should help:







http://fins.actwin.com/aquariafaq.html Click Your First Aquarium or skip the home page and go here: Practical Freshwater Chemistry
Im not sure of the age if the kits. I just bought them a week or so ago but did not look at the dates on them ( assuming they have dates on them like salifert does)

My KH is also in the 3dg range tap and RO/DI
 
Apr 2, 2002
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New York
RO/DI should be pretty much pure water. This means 0 KH and 0 GH, it means no ions like nitrate. It should be neutral pH except for the CO2 which will make it look acid. It should have no salt. Ir should have close to, or 0 TDS.

So my next question is how old is your ro/di unit and have you ever replaced the RO membrane or the DI resin?
 

Miller2112

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Nov 2, 2020
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I replace the DI resin once both DI chambers have turned orange. Right now one is getting orange and the second still looks fine. The membrane is probably 18 months old. The unit is still producing 0TDS. I usually change the membrane once i see DI resin not lasting as long. I also only ever check TDS never PH or anything else. Maybe its time for membrane
 
Apr 2, 2002
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O TDS should mean the unit is OK? But, TDS is a formula applied to the the underlying conductivity measurement actual being done. I do not have a basic feel for microsiemens but I do for TDS. My continuous monitor give me 3 choices- microsiemens, and 2 different TDS fotmulas.

But this again brings me back to this. You cannot have 0 TDS and Nitrate in the same water. The conductivity will detect ions and that is what nitrate is.

So my next question is what are you using to measure the TDS. I have both a continuous monitor and 2 inexpensive HM digital testers that also read temp. in C.
 

NicePoeci

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Oct 30, 2020
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I personally just got sick of tap water killing fish once a year and not knowing what was in my water, because it changes. Ive got 30 aquariums so it gives me peace of mind. I thinks its less expensive than tap water conditioner - especially because there are all sizes of RO units you can get anywhere from $80+ but - I think it depends on what your working with and how much you need. If you do get one just get a long hose - ive got a 50ft to get anywhere I need water. Of course you have to remineralize and stabilize it etc- but you coming from salt water probably know all about that.
 

Miller2112

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Nov 2, 2020
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I already have the unit. I do have a long line coming off of it since the unit is out in my garage.
What do you use to remineralize and stabilize it? For saltwater all trace elements are handled by the salt mix for the most part
 

fishorama

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Jun 28, 2006
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Sorry, I didn't mean to accuse you of lax ro/di maintenance. I'm just wondering why your water didn't change...shouldn't it have? My cheap HM TDS meter recently bit the dust, I haven't replaced it yet. I'm just trying to understand...
 
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