Remineralizing RO question - The Planted Tank Forum
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post #1 of 14 (permalink) Old 05-18-2020, 07:04 PM Thread Starter
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Rob at Flip Aquatics says on a YouTube post to add salty shrimp to RO water until 130tds and then you are good for bee shrimp, CRS, other caridinia, etc.

However, he says he keeps those shrimp at TDS if 130-160 and <6-7 gh. When I get 130 tds using salty shrimp, my gh is 11!

If I carved that in half, Iíd have a starting tds around 60-70, which seems awful low.

Now I know the whole book on how tds is overrated etc. Iím really asking the question to audit robs advice and see if folks think there is any issue with that. He seems to be super successful with it but the parameters donít really line up.

https://m.youtube.com/watch?v=wUbDetDVd2U

This is the video I referenced.

Iím also using RO water with a tds of 1.

Last edited by Darkblade48; 05-18-2020 at 09:56 PM. Reason: Please use the edit function for back to back posts to keep threads cleaner
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post #2 of 14 (permalink) Old 05-18-2020, 08:45 PM
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That could be more of a TDS meter needing to be calibrated than anything else... *OR* the SS doesn't dissolve the same from batch to batch.

With 11 GH, your TDS ought to be around 200... so I would recommend making sure your TDS meter is calibrated first and foremost!


at 130 TDS, the GH should be at about 7 or below.
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post #3 of 14 (permalink) Old 05-18-2020, 10:04 PM Thread Starter
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Thanks! Has anyone else had problems with tds meters being calibrated improperly? This is a new HM digital right out of the box. Dang thing is supposed to be factory calibrated &#x1f61e;
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post #4 of 14 (permalink) Old 05-18-2020, 10:16 PM
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How long after you added the SS did you measure the TDS? When I use gh/kh+ my tds will continue to rise for a few hours before I add it to the tank.


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post #5 of 14 (permalink) Old 05-18-2020, 10:34 PM
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In addition to the calibration issue (which can also involve how the calibration is performed), is your TDS meter scaled the same as his? That video is sorely lacking in describing the details of the test method. It would have been better to establish a dGH value as the control, rather than a TDS value. TDS meters can come in a variety of forms and can report many differing values. For the most part, the way we use TDS meters makes them really only useful as relative comparison points between readings we take at different times with our own meters. If you can determine what your ideal SS loading is and then take a TDS reading, you could then use that as a guide for future reference with your meter, but make sure that it is always calibrated correctly.

If you are interested in the minutiae of how TDS meters can vary, here is an article that describes it: What is TDS? by Randy Holmes-Farley - Reefkeeping.com.

If you want to see how various dissolved solids can actually add up to true ppm readings (most meters we use, in the US, in our hobby, don't measure actual ppm), you can do that here: https://www.lenntech.com/calculators...-ec_engels.htm
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post #6 of 14 (permalink) Old 05-19-2020, 02:58 AM Thread Starter
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Thanks for all the feedback. I’m using the same tester he did in the video.
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post #7 of 14 (permalink) Old 05-19-2020, 12:09 PM
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Your best bet is to ignore the advice you found on YouTube about TDS but take the general method and put it to use for yourself.

I generally mix RO/DI water in containers hours/days before I need to use it. Due to the nature of salts, dry mixes will vary with each use. So I add a little bit at a time to my container as a pump circulates water. Then I test a few minutes later. Once I get close to what I think is the sweet spot, I let things sit for an hour and then come back to test. Once I know gH (and kH, if applicable) is where I want it, then I'll use that water in my tanks.

Even with a crappy TDS meter, you should be able to find your hardness sweet spot and then use the meter to help you each time - even if it's not spitting out a reading you believe is accurate.


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post #8 of 14 (permalink) Old 05-19-2020, 01:23 PM Thread Starter
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Thanks very much. Was really hoping not to have to do a liquid test kit for every single water change. Geez. Guess that is what it is. I guess the takeaway is that the package instructions are also unreliable based on the nature of salts?

The TDS formula (i.e., add until you get a certain TDS, not necessarily testing for GH) seems a popular way to remineralize: https://www.theshrimpfarm.com/posts/...water-changes/.

Also, looks like I'm not the only one who has faced this odd "low TDS/high GH" issue with Salty Shrimp: https://www.shrimpspot.com/topic/355...lty-shrimp-gh/

Anyone faced this issue? Or do you get normal (130-150) TDS with GH of 5-6?

Last edited by Darkblade48; 05-20-2020 at 02:42 PM. Reason: Please use the edit function for back to back posts to keep threads cleaner
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post #9 of 14 (permalink) Old 05-20-2020, 03:40 AM
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When I was using SS GH/KH, I had "low" TDS levels compared to others... when I mean low, the TDS was about 18-20 TDS per every 1 GH. So if I wanted 8 GH, then the TDS would be about 150 or so. Other people would report TDS reading of 180-200+ at the same GH level.

1 GH equals 17.86 TDS.... minimum. So it's impossible to have lower than that per GH level.
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post #10 of 14 (permalink) Old 05-20-2020, 06:52 AM
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Quote:
Originally Posted by ant0328 View Post
Thanks very much. Was really hoping not to have to do a liquid test kit for every single water change. Geez. Guess that is what it is. I guess the takeaway is that the package instructions are also unreliable based on the nature of salts?
Ignore TDS, mix change water to GH desired and add a couple almond leaves and let set for at least 8-10hrs. Then test GH again and if it’s on target then measure your TDS.

Your GH test kit only measures Ca and Mg. When you test TDS it will be measuring those as well humic and fulvic acids added by leaves as well as any Fe, K etc added to water, say by adding a low dose of ferts to change water. Write down formula that got you there, what GH reading is and the TDS. Get the Ca and Mg right and hopefully SS will add the proper ratios. Once you get formula all you have to do is stick TDS pen in and verify your on target, GH testing becomes a thing of past. Also check TDS of your RO water before adding anything, if you see it rising you need to think about servicing units prefilter or maybe time for a membrane change.

Then measure you tds in tank before and after water change, write those down. Then it’s simple to measure accumulations in your tank with the TDS meter and know when to change water and if your changing enough. There are to many variables in tank plant and livestock biomass, as well as dosing, choice of substrate, rocks, wood or no wood. TDS measures everything in your water, GH helps you set just the proper Ca and Mg levels.

There is no one size fits all TDS reading but GH readings are concrete scientific readings of 2 important minerals in tank, you just have to trust the Magic Fairy dust your dumping in your water has proper ratios of all the other elements.
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post #11 of 14 (permalink) Old 05-21-2020, 04:14 PM Thread Starter
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Quote:
Originally Posted by DaveKS View Post
Ignore TDS, mix change water to GH desired and add a couple almond leaves and let set for at least 8-10hrs. Then test GH again and if itís on target then measure your TDS.

Your GH test kit only measures Ca and Mg. When you test TDS it will be measuring those as well humic and fulvic acids added by leaves as well as any Fe, K etc added to water, say by adding a low dose of ferts to change water. Write down formula that got you there, what GH reading is and the TDS. Get the Ca and Mg right and hopefully SS will add the proper ratios. Once you get formula all you have to do is stick TDS pen in and verify your on target, GH testing becomes a thing of past. Also check TDS of your RO water before adding anything, if you see it rising you need to think about servicing units prefilter or maybe time for a membrane change.

Then measure you tds in tank before and after water change, write those down. Then itís simple to measure accumulations in your tank with the TDS meter and know when to change water and if your changing enough. There are to many variables in tank plant and livestock biomass, as well as dosing, choice of substrate, rocks, wood or no wood. TDS measures everything in your water, GH helps you set just the proper Ca and Mg levels.

There is no one size fits all TDS reading but GH readings are concrete scientific readings of 2 important minerals in tank, you just have to trust the Magic Fairy dust your dumping in your water has proper ratios of all the other elements.
Thanks very much. Using fresh RO here, so the TDS reading on that is 1. RO filter is pretty good and well-serviced.

Performed some Salty Shrimp GH+ experiments that I thought were interesting. For testing used a factory-calibrated HM Digital TDS pen and API PH and GH liquid tests. This base RO water has a PH in the 6.8-7 range.

Mixed 2.5 gallons of fresh, 1 TDS, RO to 140 TDS. That resulted in an immediate GH reading of 11. Let that sit in a sealed container for two days. New GH reading was 9 (thought that was odd that it dropped, did a second test to confirm) and PH was 6.8-7.0.

Mixed 2.5 gallons of fresh, 1 TDS RO to 100 TDS. After two days, that resulted in a GH of 6 (which is about where I want to be). But the PH was at 7.6!

A couple of thoughts:

1. I understand that TDS testing in a tank is dangerous and doesn't really tell you anything because it tests for everything, but I think people use TDS in a different way when remineralizing RO water because there is nothing else (no ferts, etc.) in the RO water to start. Many folks, like Flip Aquatics and others out there that I've found, are getting a GH of 5 or 6 with a TDS of 140-150. Curious as to why mine is lower TDS. Concerned about keeping shrimp with the initial TDS of the water change water too low. I suppose GH is the only value that matters, but I do know shrimp can suffer from TDS shock, I just don't know in what range. I keep tangerine tigers so they are fairly hearty.

2. What the heck is going on with the PH in the second batch? I didn't think adding GH would swing the PH up from 6.8 to 7 to 7.6. That seems wild. Also, why did twice as much SS not swing up the first batch as much? Shouldn't the second batch, with less SS, have affected the PH less than the first batch?

One reason I wanted to remineralize RO water was to achieve very stable parameters. However, with the PH swinging up like this, only to be buffered down in my tank (active substrate), and the TDS not being nearly what others are seeing and recommend, I'm just concerned that this is not working.

Interested to hear everyone's thoughts, and thanks for those that have already commented.

Quote:
Originally Posted by DaveKS View Post
Ignore TDS, mix change water to GH desired and add a couple almond leaves and let set for at least 8-10hrs. Then test GH again and if itís on target then measure your TDS.

Your GH test kit only measures Ca and Mg. When you test TDS it will be measuring those as well humic and fulvic acids added by leaves as well as any Fe, K etc added to water, say by adding a low dose of ferts to change water. Write down formula that got you there, what GH reading is and the TDS. Get the Ca and Mg right and hopefully SS will add the proper ratios. Once you get formula all you have to do is stick TDS pen in and verify your on target, GH testing becomes a thing of past. Also check TDS of your RO water before adding anything, if you see it rising you need to think about servicing units prefilter or maybe time for a membrane change.

Then measure you tds in tank before and after water change, write those down. Then itís simple to measure accumulations in your tank with the TDS meter and know when to change water and if your changing enough. There are to many variables in tank plant and livestock biomass, as well as dosing, choice of substrate, rocks, wood or no wood. TDS measures everything in your water, GH helps you set just the proper Ca and Mg levels.

There is no one size fits all TDS reading but GH readings are concrete scientific readings of 2 important minerals in tank, you just have to trust the Magic Fairy dust your dumping in your water has proper ratios of all the other elements.
Also incredible use of "Magic Fairy dust" hahaha. That was great.

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Quote:
Originally Posted by Zoidburg View Post
When I was using SS GH/KH, I had "low" TDS levels compared to others... when I mean low, the TDS was about 18-20 TDS per every 1 GH. So if I wanted 8 GH, then the TDS would be about 150 or so. Other people would report TDS reading of 180-200+ at the same GH level.

1 GH equals 17.86 TDS.... minimum. So it's impossible to have lower than that per GH level.
Really interesting. Thanks so much. Yea, I'm just slightly south of the minimum there with a GH of 6 and TDS of 98-100.

Last edited by Darkblade48; 05-22-2020 at 01:43 PM. Reason: Please use the edit function for back to back posts to keep threads cleaner
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post #12 of 14 (permalink) Old 05-21-2020, 09:41 PM
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You cannot trust PH test or PH probes on pure RO or distilled water.

When you set out RO water into a open container it starts absorbing co2 into water, a portion of that free co2 will bind with hydrogen and become carbonic acid, H2CO3. That carbonic acid will then dissociate it’s Hydrogen ion and react with minerals in water becoming something like CaCO3. That dissociated hydrogen is then free to bind with free co2 to again form carbonic acid once more. That reaction continues to happen over and over again the next few hours, forming carbonate and bicarbonates of the various minerals you’ve added to water. When all gases and minerals in water have reached equilibrium you will finally be able to measure your waters true PH, KH and GH.

Add that water to your aquarium which will at least have a small amount of organic acids in solution and water will shift it’s Equilibrium again. That’s why I always add a small bag of peat/leaves to my change water to add a hint of organic acids to it so I can be pretty much be 100% sure that what I’m mixing up is exactly what it going to be when it hits the tank, just a cleaner version of tanks water. Same water just lower DOC and TOC content.
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Last edited by DaveKS; 05-22-2020 at 10:20 AM. Reason: Typo
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post #13 of 14 (permalink) Old 05-22-2020, 06:52 PM Thread Starter
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Quote:
Originally Posted by DaveKS View Post
You cannot trust PH test or PH probes on pure RO or distilled water.

When you set out RO water into a open container it starts absorbing co2 into water, a portion of that free co2 will bind with hydrogen and become carbonic acid, H2CO3. That carbonic acid will then dissociate itís Hydrogen ion and react with minerals in water becoming something like CaCO3. That dissociated hydrogen is then free to bind with free co2 to again form carbonic acid once more. That reaction continues to happen over and over again the next few hours, forming carbonate and bicarbonates of the various minerals youíve added to water. When all gases and minerals in water have reached equilibrium you will finally be able to measure your waters true PH, KH and GH.

Add that water to your aquarium which will at least have a small amount of organic acids in solution and water will shift itís Equilibrium again. Thatís why I always add a small bag of peat/leaves to my change water to add a hint of organic acids to it so I can be pretty much be 100% sure that what Iím mixing up is exactly what it going to be when it hits the tank, just a cleaner version of tanks water. Same water just lower DOC and TOC content.
UPDATE: I have let the second batch of water sit for five days. The ph still reads 7.6. The product says it does not directly influence ph, but it clearly does.
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post #14 of 14 (permalink) Old 05-29-2020, 09:02 PM Thread Starter
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Setting aside all the ph issues, I bought some calibration solution. TDS meter is perfectly calibrated. Still getting the low tds reading.
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