Getting from straight R/O to healthy aquarium water - The Planted Tank Forum
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post #1 of 29 (permalink) Old 10-14-2015, 07:29 PM Thread Starter
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Getting from straight R/O to healthy aquarium water

Let's say your only feasible source of water for your aquarium is reverse-osmosis filtered water with 0 GH and 0-1 KH (using API's test kit, which I'm told tests for total alkalinity?). What is the best way to get from there to water that's healthy and stable for fish and plants, particularly for fish that won't tolerate high pH levels?

For GH: This part seems straightforward. Seachem Equilibrium or similar products seem like a good bet to add back calcium, magnesium, etc., and you can just add as much as you need to get to the recommended levels for your fish and plants.

For KH/total alkalinity: This is where I lose my mind. Starting from 0 KH/alkalinity, what do you do to get to relatively stable KH and PH levels that will work for your flora and fauna? For fish that thrive in high pH/KH, Rift Lake buffers, baking soda, etc. seem like viable solutions. But what about for soft- or blackwater fish that aren't going to do well in 8+ pH? If you have almost no KH/total alkalinity from your source, and you add something like baking soda or Seachem Alkaline Buffer as a buffer, pH goes up quite a bit, i.e., it buffers against pH swings, but keeps pH at a relatively high level. But if you don't add any sort of buffer to increase KH/total alkalinity, isn't a KH of 0-1 going to leave you susceptible to wild pH swings? Is there something you can do to buffer against pH swings while keeping pH neutral to slightly acidic? Seachem offers products like Acid Regulator, Neutral Regulator, etc.... but the array of products and the descriptions of how they work leave my head spinning.

Anyone have a science-based answer to this along with a recommendation?


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post #2 of 29 (permalink) Old 10-14-2015, 10:10 PM
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I use equilibrium and the alkaline buffer. I add the buffer until my ph tests at 7.0. Then I use co2 to get a 1.0 drop, down to a pH of 6.0.

How low are you looking to go with pH? The pH of straight RO for me is well below the neutral, 7.0. I believe I'm in the 4-6 dKh rating after adding enough of the alkaline buffer to get the water up to 7.0.
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post #3 of 29 (permalink) Old 10-14-2015, 10:20 PM
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Most folks just blend tap with the RO to get a specific KH.

Say the tap is 10 and the RO is close to 0, then you blend say 25% tap with 75% RO for the water change.
KH is now 2.5.

Saves a lot of RO water that way.




Regards,
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post #4 of 29 (permalink) Old 10-14-2015, 10:34 PM Thread Starter
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Getting from straight R/O to healthy aquarium water

Quote:
Originally Posted by plantbrain View Post
Most folks just blend tap with the RO to get a specific KH.



Say the tap is 10 and the RO is close to 0, then you blend say 25% tap with 75% RO for the water change.

KH is now 2.5.



Saves a lot of RO water that way.

Thanks Tom. I can't use tap unfortunately, because it all goes through a water softener (even outside spigots) I've consistently read that's not good for plants or fish, and the water post-softener reads as 0 degrees KH anyway. So I'm stuck with adding back minerals and buffers to straight RO, and trying to find a way to do it that will result in a stable pH that is acidic or at least not much over 7. Seachem Equilibrium and Acid/Neutral Regulators seem like the best options for that so far... Unless I'm just wrong about the dangers of 0 degree KH.


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post #5 of 29 (permalink) Old 10-15-2015, 12:56 AM
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I was using half RO and half tap water, but became a little concerned about what dissolved metals might be in the tap water. So, I've been experimenting with re-mineralizing RO water with http://smile.amazon.com/gp/product/B0002A5WQA?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00 for GH and http://smile.amazon.com/gp/product/B0064GZPU4?psc=1&redirect=true&ref_=od_aui_detailpages00 for KH. It has been working well.
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post #6 of 29 (permalink) Old 10-15-2015, 01:13 AM Thread Starter
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Quote:
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I was using half RO and half tap water, but became a little concerned about what dissolved metals might be in the tap water. So, I've been experimenting with re-mineralizing RO water with Seachem Equilibrium for GH and potassium bicarbonate for KH. It has been working well.

How much potassium bicarbonate, and what pH range does it give you?


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post #7 of 29 (permalink) Old 10-15-2015, 01:39 AM
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1.4 grams per 10 gallons will yield an increase of 1 dKH. This will also add 14ppm of potassium.

All carbonate sources will want to buffer at a pH above 7.0. You need to have carbonate sources to maintain balance, so to offset the carbonate effect on pH, and lower pH, the solution is to add acid sources to compensate, were the balance of acid and alkaline give you the desired pH.

Feel free to edit.
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post #8 of 29 (permalink) Old 10-15-2015, 02:46 AM
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Quote:
Originally Posted by end3r.P View Post
How much potassium bicarbonate, and what pH range does it give you?
About 5 min. almost empties my RO reservoir. That is somewhere around 1.25-1.5 gal. I think. To that I add 1/2 tsp. of potassium bicarbonate and 1 tsp. of Equilibrium. Then I test GH and KH to make sure they are both about 5 dkh and TDS is close to the tank value. I don't bother with pH.

I made the mistake of trying to control pH with chemicals (pH Down) and just stressed the fish. Lost some corys and otos that way.
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post #9 of 29 (permalink) Old 10-15-2015, 02:51 AM
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In general, you will find it is easier to maintain stability if you don't try to add acid to "fix" the PH from adding alkalinity. Yes, there are "acid buffers" you can add, but the natural (as in what you see in nature generally) approach is that the dKH determines the PH. The aquarium will reach equilibrium with air's CO2 (usually around 3ppm), and this be controlled by the dKH. Near zero dKH in RODI water and you get very acidic water (like 5.5 +/-, and no pure water in an open top tank is not at ph=7). As you get near dKH=1 or so you get near ph=7, and as it increases you get higher and higher PH.

If you are going for near neutral, just experiment a bit starting at about dKH=1 and see where you land (it will vary based on your situation, aeration, take contents). Add a bit more baking soda to get a bit higher, withhold (but don't withhold it all) to get lower PH. I've also found Equlibrium adds dKH as well, even though it is not supposed to, so getting high dGH and low dKH is not easy.

Yes, you can add acids to lower the ph, but all tend to have some side effect, from being temporary to changing the chemistry otherwise.

Incidentally, good old baking soda which you can buy by the 5 pounds for a few bucks is just fine for alkalinity. There's a ton of potassium already in Equilibrium.

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post #10 of 29 (permalink) Old 10-15-2015, 02:55 AM
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Here is how I do this:

1) Set the GH to suit the fish. (Seachem Equilibrium), most soft water fish, about 3 degrees.
2) Make the KH match the GH. (Baking soda: 1 teaspoon per 30 gallons = 2 German degrees of hardness) or potassium bicarbonate as above.
3) For black water fish circulate the water with peat moss (Knee-hi stocking per garbage can of water. 'Garbage can' could be 20-40 gallons- I have several)
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post #11 of 29 (permalink) Old 10-15-2015, 02:55 AM
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PS. A typical mix for me for 10 gallons is 0.18 tsp Baking Soda (i.e. a quarter tsp measure a bit over half full, very little), and 1.5tsp of Equilibrium. This should be dKH=1 but seems to land about 2+, and a dGH of about 3, and PH in the 7.2-7.4 range. This is in RODI water. You're saying RO water, which may already have stuff in it if you mean it literally.

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post #12 of 29 (permalink) Old 10-15-2015, 03:38 AM
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The pH is less important to the fish than the mineral levels.
Get the GH and KH right, and don't worry about the pH. When GH and KH are in the right range, the pH will likely be in the right range, too.
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post #13 of 29 (permalink) Old 10-15-2015, 04:27 AM
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Quote:
Originally Posted by Linwood View Post
Yes, you can add acids to lower the ph, but all tend to have some side effect, from being temporary to changing the chemistry otherwise. .
Carbonates can (and) do the exact same thing.

The only difference between carbonate buffers and acid buffers (apart from the obvious effects on pH) is the level of knowledge parroted through the industry.

Feel free to edit.

Last edited by Audionut; 10-15-2015 at 04:39 AM. Reason: Remove off-topic
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post #14 of 29 (permalink) Old 10-15-2015, 03:52 PM Thread Starter
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The main thing I don't understand is that many if not all solutions to stabilizing pH at neutral or acidic levels with low/no-KH source water include adding both an alkaline buffer (baking soda, Seachem Alkaline Buffer, etc.) AND what amounts to an acid buffer (peat, Indian almond leaves, Seachem Acid Buffer/Regulator, etc.). To my not-chemist brain, it seems like these would just cancel each other out, leaving you with still-unbuffered water subject to big pH swings. But I'm thinking that's not true, i.e., that you can add both, and each will buffer against pH swings in the opposite direction (alkaline buffers protect against pH drops, acid buffers protect against pH increases), and that the resulting pH is (at least in part) a function of the proportions of the two buffers used. Put another way, when you add an acid buffer (as opposed to, say, straight acid?) it drops pH some, but doesn't "eat away" the alkaline buffer, at least not entirely. So you can have an acidic or neutral pH with a low but non-zero alkalinity/KH. Maybe.

The science behind any of this, of course, is mud to me right now.


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post #15 of 29 (permalink) Old 10-15-2015, 04:07 PM
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There is an equilibrium point between acid and alkaline buffers. This equilibrium point determines the pH.

What pH doesn't describe is the amount of buffers in the water. We can reach the same equilibrium point (the same pH), with a little acid buffer and a little alkaline buffer. We can also reach the same equilibrium point with lots of acid buffer, and lots of alkaline buffer.

The equilibrium point (pH) is like a ratio. You can have the same ratio with vastly different amounts of total content. One banana, and one orange have a ratio of one banana to one orange, or 50/50. Three trillion bananas and three trillion oranges have the same 50/50 ratio.

Acid buffers will deplete alkaline buffers, but you need to understand the above first.

Feel free to edit.

Last edited by Audionut; 10-15-2015 at 04:32 PM. Reason: Mmmmm, bananas!!!
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