Ratio of RO water to tap water

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milalic
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Ratio of RO water to tap water

Post by milalic »

I decided to get an RO unit. My ph is ~7.9-8.1 and total hardness is ~200-250ppm.

I currently have a 75G tank, 58G tank, and two 10G tanks...if I want to achive softwater and a ph of around 6.8-7.2, what ratio of RO:tap water do you suggest?

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Post by fishgeek »

r/o unit will remove roughly 95% of dissolved solids so straight r/o water should read at about 5% f your previous hardness
so say roughly 10-12 ppm total hardness

this water will probably have a pH similar to what it started at , though measuring the pH of water that is getting close to pure is extremely hard to do accurately

what type of shrimp are you intending to keep in it?

i use peat to manipulate my water for pH though i think other's here may suggest that is not ideal for shrimp
i do it primarily for my apisto's and as yet have not bred any soft water shrimp

andrew
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Post by badflash »

You need to measure what comes out of your R/O unit and then do a little algebra to mix it. The basic formula is:

{(PPM A X Gallons A)+(PPM B X Gallons B)}/(Gallons A+Gallons B)

If this is too complicated then just add pure R/O water and a 1/4 teaspoon of R/O right per 10 gallons.
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Post by Mustafa »

As fishgeek already said, your ph might not change all that much at all depending on your water supply. You will have to use acid to control the ph accurately. Fishgeek uses peat, which *might* work for shrimp but hydrochloric acid (muriatic acid) works for sure. Search for how to use it in this forum as it has been discussed. With your water parameters I would suggest a 80:20 ratio or RO and tap water respectively.
Last edited by Mustafa on Wed Apr 12, 2006 12:55 pm, edited 1 time in total.
milalic
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Post by milalic »

fishgeek wrote: this water will probably have a pH similar to what it started at , though measuring the pH of water that is getting close to pure is extremely hard to do accurately
andrew
What determines if the ph is going to be around the same or not when the water goes through the RO unit?

Thanks
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Post by GunmetalBlue »

As to your above question, someone else may better be able to answer it, but I think Mustafa said if your city adds things like sodium hydroxide, it can affect the pH.

Milalic, hope you won't mind my answering some of your other questions here, as it might be helpful for anyone else wanting to go the muriatic acid route.

I think right now, you might be overthinking it. You'll find that everything will come together once you get your reliable pH meter (has that been done yet?) and start treating your water. It is then that you'll find out what work needs to be done in terms of how often and how much muriatic acid to add.

The process is actually really simple once you get going: Create a particular pH target for a tank, then add a drop or two (or more, depending on tank size) and keep rechecking the pH till it drops to your intended target. It's that simple. The requirement though, is that at first, until you GAIN EXPERIENCE and get the feel of how your water responds, you have to be right on it and add a drop of muriatic every time the pH goes back up.

Regarding water change water, I usually match my WC water to the tank I'm adding it to, so in other words, if the WC water's pH is 7.5 and my shrimp tank is 6.8, I just add muriatic acid to the WC water until it matches the tank's, just before the WC. But that doesn't mean I discontinue checking the pH in the tanks daily - I still check every day.

As to white distilled vinegar, I have no experience nor would I personally bother, but that's up to you - like if you did research on it and thought it better for you. Muriatic acid is just too easy and too convenient. I'm not trying to downplay muriatic acid though, you do have to use it with a lot of responsibility.

If you still feel anxious about the muriatic acid method, try it out on a test tank OR approach it the way I did - taking the pH down in slow, incremental steps, so as not to have big pH swings on the up side. Once the acid starts eating up the akaline, the pH will start to stay down. After that, you'll only have to use it every once in a while.

-GB
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Post by fishgeek »

the pH of r/o water should in theory be neutral

what determines the pH well if you like chemistry it is the hydroxyl ion versus hydrogen ion balance that is responsible for this

in pure water there is nothing to bind with either H+ nor OH- so you only have either H2O or equal numbers of hydrogen and hydroxtl ions
balanced or neutral pH

once other things are added to the water they either bind with the -OH and allow more H+ ions to cause an acidic state or lower pH
and the reverse also occurs certain products will bind with H+ ions

carbonates will bind to hydrogen ions holding any acid changes until they are all used up(as badflash was talking about with the acid)

there are lots of sites with water chemistry at whatever level you want to get into it
best way is to see what your water and your r/o does
prehaps your water will come out neutral and you wont need to play with adjusting pH too much

have fun
andrew
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Post by badflash »

Some towns use Sodium Hydroxide in the water for a basic pH. This goes through the R/O membrane. Muratic acid works really well on this.

In my case the issue was just contamination of my substrate. After i burned this out there were no further issues. It took several weeks to get there, but has been rock steady since. I think you end up with a bacteria that buffers your pH to a fixed point if you fight it long enough. I have two tanks set up with the same substate- white sand. One I acidified to a pH of 6.4 and it sems to be locked in. I have another that seems locked in at 8.2 and I can't budge it. The shrimp in each tank are appropriate to the pH so I'm going with it.
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Post by Mustafa »

GunmetalBlue wrote:As to white distilled vinegar, I have no experience nor would I personally bother, but that's up to you - like if you did research on it and thought it better for you.
I can tell you guys right now that vinegar not only does not work (leaves alkalinity alone instead of eating away at it like HCL and thus only creates a temporary ph drop) but will also kill your shrimp. The vinegar causes a huge bacteria bloom which your shrimp succumb to. All organic acids (i.e. acetic acid ( in vinegar), citric acid (part of lemon juice) etc.) will feed bacteria which will organically overload your tank. When it comes to acids to lower your ph, hydrochloric acid is really the best way to go.
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Post by milalic »

All,

Thanks for your responses. Everything is on its way. THe ph meter, the ro/unit. I will go the muriatric acid way.

One more question, does the HCL adds TDS to the water?


Cheers,
PEdro
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Post by badflash »

does the HCL adds TDS to the water?
When HCl reacts with a base the normal product is a salt and water. The compound it is reacting with is already in the water, so I think you are just changing what is there, not adding much. I have not seen a change in the TDS, and in some cases havew seen a decrease. When HCl reacts with a carbonate, it produces CO2 and calcium chroride.
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