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post #1 of 7 (permalink) Old 01-31-2013, 07:34 PM Thread Starter
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Home RO unit - does it affect PH?

I contacted Air Water Ice (AWI) and asked them if their units change the PH of the water put through it. They wrote back and said no one has asked this, and they did not know.

I am considering cutting my well water with RO. I bought some at the local grocery to test.

We buy distilled water to make coffee, ice, for drinking water. Our well water is "very hard," and PH is between 8 and 8.4 depending on test kit used. Coffee pot plugs up quickly, white scum on all the pots used to boil noodles etc. So, we could use an RO unit anyway. Since I started up the aquarium in October, it's been a nightmare keeping the hard water scum off glass canopy, out of filter tubes, off the tank glass, off the heater glass.

I found if I use 2 parts RO to 1 part well water, my PH dropped to 7.4, and the GH to 185ppm, or German Degree 10.3, KH to 143ppm or German degree 7.98.

Straight well water, with the API GH/KH liquid test takes 26 drops to change color. Cut 2/3 with RO, it took 10 drops for GH and 8 drops for KH, which seems like it is getting my well water into a much better range for fish.

If any of you have an RO unit at home, could you tell me if it lowers the PH? Would someone mind testing their water if they don't know? I don't want to invest in an RO unit only to find that the reason the RO water I am buying has a more neutral PH of 7 is that it is made from city water in nearby town, and not as high a PH as the well water I have.

I have 6 neons that have survived a few weeks, but I really like them in my planted tank, and would like to add 10 more. At $4.99 each at the local fish store, I'd like them to live if I make that kind of investment!

Last edited by daylily; 01-31-2013 at 07:35 PM. Reason: spelling
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post #2 of 7 (permalink) Old 01-31-2013, 07:47 PM
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The water coming out of the unit will be very close to a ph of 7.

It will also have next to no buffering capacity, so from there it will swing easily anywhere you like, depending on what you add.

Adding it to your well water should have the effect of diluting the OH ions that are making your water basic... so it will move the overall pH toward 7.

That being said, about all the recommendations I've seen say start with RO water and then buffer it.... so I'd conceptually start with your RO water, then add well water and see what happens as you add well water. If it goes where you want it to, great. If it doesn't you may be stuck buying a product to put the water where you want it.
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post #3 of 7 (permalink) Old 01-31-2013, 08:10 PM
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i had well water at my house and my PH was around 7.6 and the PH of my RO water was around 6.2. so for me it was a pretty significant change

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post #4 of 7 (permalink) Old 01-31-2013, 11:28 PM Thread Starter
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Thanks for your replies!

I had another email from AWI - I don't want to copy paste it without permission - but they did look up more info for me. They say the So. California water they had test results on started at 8.12 going in to the system and 8.06 after RO unit, so they conclude it has little effect on PH.

It would also depend on the composition and gasses in the "input water supply"...

I'd hate to buy the unit, pay to have it installed, then end up without having the PH change. I'm not sure it would be worth it to change the GH and KH alone. I suppose it would eliminate all the scale buildup though.

Anyone else with high PH, GH and KH have any additional info on if it lowered the PH of your water?
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post #5 of 7 (permalink) Old 01-31-2013, 11:54 PM
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I have all three.

And, I don't mess with the water... I age it & use it the way it comes out of my tap. KH around 7 deg, GH around 11 deg, PH around 8.2. In my noob days I tried the "pH down" stuff and no matter how much I dumped in (it seemed) the next day it was right back to 8 - 8.2. My fish got a lot happier when I just stopped messing with it.

The RO is really about buffering. Hard water like that is super hard to move... because the mineral ions tend to suck up anything you put in the water to move the PH. The RO water starts you with a "clean slate" so then you can add what you want, and you don't have to worry about things you don't want being there.

Bottom line: If you really want to manipulate your water chemistry, the best way to do it is to start with RO/DI water, and then add product/minerals to put it where you want it.

My long-term advice: live with the water the way you have it. Don't buy livestock that require really soft water, quarantine, accept the fact that losses when you get fish are a part of the deal, and focus on getting a good bio filter going. In my experience, fresh water success is all about bio filtration, bio filtration, and more bio filtration.
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post #6 of 7 (permalink) Old 02-01-2013, 02:31 AM Thread Starter
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I found an explanation on converting the number of drops of the API kit to degrees and ppm. One drop = one German degree and if I multiply the drops by 17.9 I get the ppm.

My KH and GH tests on my well water both took 26 drops to change color. I also had it checked by a local fish club member, and by the local fish specialty store with similar results.

So, KH and GH would be 26 degrees hardness, or 465.4 ppm

My PH is at the highest range of the "lower" PH test in the Freshwater Master kit - and if I use the High Range PH test, it is hard to tell, but somewhere between 7.8 and 8.2. The local fish club guy tested it with a better test kit and said 8.2 to 8.4

Not much can live in that. Knowing how hard the water is, and how alkaline, kept me from even trying an aquarium for nearly 30 years. I'm really not into livebearers or brackish type fish, although I did briefly consider a puffer.

I've got a betta in a 5 gal Fluval Spec V that seems to be doing fine, but the ends of his fins look funny - someone on a betta breeding forum told me, before I even got the betta - that the fin edges can be affected by high PH, but that it won't really affect the health of the betta.

The other fish, shrimp, snails are in a 15 gallon.

I am having issues with a lot of the plants too - the fish club person gave me at least 20 different varieties to try and see what would live. While many are still living - few are thriving.

So, if I use the 2/3 RO to 1/3 well water, I get
PH 7.2 to 7.4
GH 10.3 degrees or 185 ppm
KH 7.9 degrees or 143 ppm

I thought I should mix up more of it, leave it sit for a week or two, and test a few times to see if all the numbers remain stable.

It is my understanding that using a mix of RO and well water will be easier to get to remain stable than using RO and adding stuff to it.

I did purchase PH Down when I bought the Fluval - aquarium store guy said I would need it - but after looking it up I have not used it. The info I found said similar to your experience, that it is only temporarily down.... and my understanding is that we want it to be stable no matter the number.

I'm sure it would be better to go with the well water as is, then find fish and plants that can work in it - but from all the reading I have done - there is not a lot of choice with how hard my water is and the high PH.
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post #7 of 7 (permalink) Old 02-01-2013, 04:13 PM Thread Starter
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You mention the importance of filtration.

On the 5 gal Fluval Spec V - I am using the system that came with it, but instead of carbon and biospheres in the sponge, I have 2 bags of biospheres. It is also planted, but with slower growing low light plants. It only has the Betta in it. I have a sponge covering the filter out flow, but I take it off for an hour a day to help increase flow.

The 15 has 2 Aqua Clear HOB filters for 20 gal tanks. When I had one, with all the plants, it didn't seem to me to be having a good flow around the tank, so a couple weeks ago, I added another one just like it. The original filter has carbon and biospheres in the sponge. The new one has biospheres and Purigen. I run both on "low" because other wise my fish hide in the plants (neons, pygmy cory and 2 male Endlers).

Would you say that is enough filtration?

In the 15 - I think I have to much light. The lights are 12" from substrate, and it's a 20" T5HO with one 6000k and one 650nm bulb. I had replaced the 650 with a full spectrum 10000k but the guy I got my plants from at the local club told me to try taking one of the bulbs out. The fixture won't turn on with only one bulb, so I put the lower bulb back in. There is a big mixture of plants in it, so time will tell. I'm wondering if I need to think about Co2... but that is another post. If I understand correctly, Co2 will help lower PH, but I worry about power outages. Last summer we were without power for almost a week, and a few years ago, almost 2 weeks during winter. I have a battery bubbler, and keep lots of jugs of water filled up, but how would I operate Co2 without power.... one of the reasons I didn't want to do it.
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