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Discussion Starter · #1 ·
I’m debating if I want to switch from tap water to rodi water. My main concern, is that I might shock the fish/shrimp I have when I do the water changes, since I don’t have the space for a mixing vat. I do weekly 10 gallon water changes on my 20L, and while it wasn’t a problem when I was in college, I’m trying to be a better aquarist.

If I switch to RODI, I’d probably dump in all 10 gallons of rodi first, and then add a slurry of equilibrium, acid buffer, and alkaline buffer to the water.

What I do currently, is measure the tds of the tap water, and add rodi water as necessary to bring it down to 150 ppm.
 

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I’m debating if I want to switch from tap water to rodi water. My main concern, is that I might shock the fish/shrimp I have when I do the water changes, since I don’t have the space for a mixing vat. I do weekly 10 gallon water changes on my 20L, and while it wasn’t a problem when I was in college, I’m trying to be a better aquarist.

If I switch to RODI, I’d probably dump in all 10 gallons of rodi first, and then add a slurry of equilibrium, acid buffer, and alkaline buffer to the water.

What I do currently, is measure the tds of the tap water, and add rodi water as necessary to bring it down to 150 ppm.
Oh so this is how people are getting their water down to 150 TDS. They do it by ruthlessly adding RO water. I've been wondering about this. My TDS is ~350 ppm. That's while using RO water remineralized to 6 dGH for the shrimp.

I have two five gallon bottles and a five gallon bucket. The five gallon bucket lives outside. I use the five gallon bucket to mix my RO water with a powerhead then I pour it into the bottles. I use the same bucket for water changes. It's not a super clean bucket but so far I haven't suffered any consequences that I know of. They make wide mouth five gallon bottles if you don't have room for a bucket.

Why do we add both acid buffer and alkaline buffer? I'm just curious, trying to learn, not being judgemental. You're not the only one doing this. Don't they counteract each other? I add Potassium Bicarbonate for 2 degrees Alkalinty then I counteract it with CO2, the acid from nitrification and Fulvic Acid from Catappa leaves. My reasons are different though. I cause Alkalinity to support nitrification because that's what fisheries do. I add Fulvic Acid to make the fish happy.

I think if you predissolve the Equilibrium you could add it at the beginning or during your water change. Premixing your RO water then dripping it in with airline would be better if you have sensitive species of shrimp. I do fifty percent water changes so I might start doing this for my recently acquired Amano Shrimp.

Keep trying to be a better aquarist. That's a good hobby ethic.
 

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Oh so this is how people are getting their water down to 150 TDS. They do it by ruthlessly adding RO water. I've been wondering about this. My TDS is ~350 ppm. That's while using RO water remineralized to 6 dGH for the shrimp.
@ichthyogeek is using RO water to dilute tap water, but that's not the only way to get low TDS. A lot people with low TDS are starting with soft water or RO water and just aren't adding as much fertilizer at one time. My plain ol' city water is 65 out of the tap and with remineralization and fertilizers and everything I end up around 185. (I could probably go lower if I was willing to tweak more, but it's not a priority.) If you want a lower TDS you could definitely change up your practices to get there, but you might need to dose leaner and/or change to dosing more often.
 

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@ichthyogeek is using RO water to dilute tap water, but that's not the only way to get low TDS. A lot people with low TDS are starting with soft water or RO water and just aren't adding as much fertilizer at one time. My plain ol' city water is 65 out of the tap and with remineralization and fertilizers and everything I end up around 185. (I could probably go lower if I was willing to tweak more, but it's not a priority.) If you want a lower TDS you could definitely change up your practices to get there, but you might need to dose leaner and/or change to dosing more often.
Oh I see. It's a combination of guerrilla tactics. Interesting. I thought I would start by getting rid of old pieces of driftwood.
 

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Oh I see. It's a combination of guerrilla tactics. Interesting. I thought I would start by getting rid of old pieces of driftwood.
I'm not sure my pretty ordinary advice to just add less stuff to your water counts as "guerrilla tactics" 😂 I didn't have a TDS pen until a few months ago, so I had no idea what I was running at. I got the pen, checked my water, decided it was fine and kept doing the same thing I was before. I love using the pen though. I'm a big fan of not chasing water parameters without a very, very good reason - maybe 350 is fine for you, especially if it's a lot of tannins? (Sorry for the thread hijack @ichthyogeek! I hope someone can answer your question.)
 

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Discussion Starter · #7 ·
It always depends on what you're keeping. Because I'm keeping softwater fish with amano shrimp, I'm aiming for 150ppm, since that's on the lower end that amanos are supposed to be able to withstand. My tap water comes out at 180-200ppm, so I usually dilute it somewhere along a 1:3 ratio (1 part RODI to 3 parts tap).

The way I learned it, was that you add acid and alkaline buffer in order to buffer the water to a specific KH and a specific pH. If you're using tap water, that's a different story, since you're dealing with predissolved buffers which requires some experimentation. But with RODI water, if you add acid buffer, you're just going to bring the water down to whatever the buffer naturally buffers to (for example, if I was using sodium acetate to buffer the water, acetic acid would cause the water to hover around 4.76).

These silly chili rasboras are so worth it, but at the same time, causing me such a headache with their weak kidneys...
 

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The way I learned it, was that you add acid and alkaline buffer in order to buffer the water to a specific KH and a specific pH.
I haven't been remineralizing RO water very long. There's more to it than I thought. I don't have the Seachem buffers. So far I've only been using Potassium Bicarbonate. How do you know what pH to set? Is that species dependent?
 

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Discussion Starter · #9 ·
I haven't been remineralizing RO water very long. There's more to it than I thought. I don't have the Seachem buffers. So far I've only been using Potassium Bicarbonate. How do you know what pH to set? Is that species dependent?
So I aim for pH and KH with the Seachem Buffers, since that's what they affect. It's mostly species dependent. For example, with my chili rasboras, I'm going to go for a pH of 6.0 or 6.5 or so, since they're used to rather acidic water. And most plants will do fine in that pH of water as well.
 

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So I aim for pH and KH with the Seachem Buffers, since that's what they affect. It's mostly species dependent. For example, with my chili rasboras, I'm going to go for a pH of 6.0 or 6.5 or so, since they're used to rather acidic water. And most plants will do fine in that pH of water as well.
So far I have only adjusted the GH to suit species. I'll check what pH they like next and adjust that if I can. I think I'll just keep it below 7.5 pH with the CO2 off for the shrimp. Thanks for explaining how and why.
 

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Well, not a lot of tannins. Are you TDS shaming me? :cry: @Deanna said I could go to 25 ppm.
25ppm Fulvic Acid (95mg / gallon) will add about 8% TDS (500 scale).

Also, be aware that plants uptake nutrients, optimally, in the pH 5.8-6.2 region and most tropical fish have no problem with this, particularly if it is CO2 driven. Unless you have fish that are known to REQUIRE a certain pH, I wouldn't be concerned about any pH between 5.0-8.0 (shrimp may have issues). Additionally, if you keep it below 7.0, you won't need to worry about ammonia, since it will all be in the safe ammonium form.

I don't add significant quantites of weak acid buffers (which are very temporary and can cause misleading KH test results), but do add bicarbonate (KHCO3) to raise pH into the optimal pH region for my RODI water. My dKH is around 1-1.2, but plants actually prefer low KH, such as this, and even lower (down to zero) and fish have no issues. Remember that what our hobby calls KH is not actually carbonate hardness (true KH) it is actually alkalinity (buffering capability) that is being measured. So, adjusting KH is what moves pH, unless weak acids (acetic, tannins, citric, etc.) are too prevalent, resulting in skewed KH readings, but these are not usually heavy enough in our typical doses.
 

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With continuous CO2 and dKH below 2, there is a problem with the PH dropping too much at night. It can be avoided by using a digital PH controller, of course.
CO2 24/7 actually creates highly stable pH, particularly if gas exchange is high (which is ideal for both CO2 and O2). I run CO2 24/7 and pH is rock solid 24/7. If you are thinking that the pH drops due to an absence of photosynthesis, high gas exchange far outstrips plant consumption of CO2 and is what provides the high stability.
 
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CO2 24/7 actually creates highly stable pH, particularly if gas exchange is high (which is ideal for both CO2 and O2). I run CO2 24/7 and pH is rock solid 24/7. If you are thinking that the pH drops due to an absence of photosynthesis, high gas exchange far outstrips plant consumption of CO2 and is what provides the high stability.
Agree. But my question is: Using a digital PH controller, or just keeping a low dose of CO2 ?.
In my case, with a controller, I observe how during photosynthesis I need much more CO2 so that the PH does not rise and at night I barely dose CO2. It is also true that I have 2-3 dKH, usually.

CO2 24/7 actually creates highly stable pH, particularly if gas exchange is high (which is ideal for both CO2 and O2). I run CO2 24/7 and pH is rock solid 24/7. If you are thinking that the pH drops due to an absence of photosynthesis, high gas exchange far outstrips plant consumption of CO2 and is what provides the high stability.
Regarding the movement of water, exchange 02 and CO2, I strongly agree, but if you are looking for a very accelerated aquarium, therefore with approximately 30 mg / l of CO2, and you have a very strong gas exchange, for a dKH 4 , and a PH 6.6, the volume of CO2 to be injected must be very high. But hey, everything consists of finding the balance, which you, evidently, have achieved. Congratulations!!
 

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Agree. But my question is: Using a digital PH controller, or just keeping a low dose of CO2 ?.
In my case, with a controller, I observe how during photosynthesis I need much more CO2 so that the PH does not rise and at night I barely dose CO2. It is also true that I have 2-3 dKH, usually.


Regarding the movement of water, exchange 02 and CO2, I strongly agree, but if you are looking for a very accelerated aquarium, therefore with approximately 30 mg / l of CO2, and you have a very strong gas exchange, for a dKH 4 , and a PH 6.6, the volume of CO2 to be injected must be very high. But hey, everything consists of finding the balance, which you, evidently, have achieved. Congratulations!!
I’m not quite sure what the question is. If you wish to re-phrase it, I’ll be happy to respond. Below, I’ve copied some comments about my use of CO2 24/7 from past postings. Perhaps an answer to your question lies somewhere in there:

I have come to the conclusion that plants use very little CO2 as a percentage of total CO2 in solution. The only thing that seems to affect CO2 levels, as we are able measure them, is by changing CO2 input and/or surface agitation.

I think that CO2 is much like other nutrients, such as Ca or K: plants don’t use that much of it, but they seem to like having a lot of it around. I suppose that this is because their uptake mechanisms just can’t get enough to fully satisfy at the apparently very low levels that make a difference between health levels. For example; since we can’t (at least, I can’t) detect even a .1 difference in pH due to CO2 consumption, let’s say that plants only use, at most, 1% of the CO2 at ideal health, and must have 30ppm to get that 1%. I haven’t found that more than 30ppm helps plants significantly, but less than that .3ppm (1% of 30ppm) would quickly start to affect things. This also implies that circulation is very important to ensure saturation along the plant surfaces.

I also have noted that running CO2 24/7 uses less total CO2 to maintain the same CO2 level. As soon as ambient light enters the room in the AM, plants can begin photosynthesis. Having said all of this, I've also run on a timer and see no large difference between the two in plant performance but, since I use less CO2 with 24/7 and the other issues, I see no reason to revert to timing the CO2 - nature doesn't do it.

It is recommended that heat pumps (of which I am cursed of having) be run with very little changing of the thermostat night and day. Maintaining a consistent temperature, as opposed to letting it drop 10 degrees at night while sleeping, uses far less electricity than trying to bring it back up in the morning. Pushing CO2 into saturation is similar and, I believe, is the main reason that I make fewer trips to the CO2 store when running 24/7. In a sense, it is much like a passive reactor, where the same amount of CO2 is always available to the plants, but higher saturation levels are possible with pressurized.

Less simple reasons:

There are subtle issues that, I believe, are also helped and it is all mainly about maintaining stable parameters. These are beliefs that I have based upon many things.
  • preventing ph from rising above 7, as it would at night in my case, prevents possible additional stress on my fish due to NH4 changing to NH3.
  • algae love unstable CO2, especially BBA (water changes are a little scary, but I do them because the benefits outweigh the risks and I do them during the siesta). If my pH moves half a point twice a day, that’s about a 20ppm CO2 move.
  • conversely, plants don’t like unstable CO2 and, therefore, may be slightly weakened.
  • nutrient uptake is optimal in the low 6’s, pH wise.
  • chelated minerals may oxidize and precipitate out, making them unavailable to plants during the day.

So, if all of our plants (including C4-type plants that have accumulated CO2 at night) and algae begin photosynthesis as soon as ambient light from the room reaches them, which has been shown, I should have to start the CO2 up at around 4-5AM. This leaves little time for CO2 being off to make much difference.

Having said all of the above, I've run it both ways and, although my tank is nearly perfect (to me), now vs. years ago when I shut it off at night, I can't say that it is due only, or even largely, to runnig CO2 24/7. Running 24/7 just to save a couple dollars a year on CO2 is not the reason that I do it. It is just a side observation.
 
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Sorry, @ichthyogeek, I didn’t realize that you didn’t have an answer to your OP. These sidebars are the way threads go, sometimes, and what can keep it interesting for many of us.

Your inhabitants prefer a softer GH and have a fairly wide range of pH (if you are injecting CO2, pH changes won’t affect your inhabitants). You seem to be saying that you are willing to go 100% RODI. Is this correct or do you want to cut tap water with it? In any case, until we got more into it, I think that your primary focus should be GH, which will drive the bulk of your TDS concerns. I don’t see any reason for acid buffers/reducers if you can use RODI.

Yes, I do remineralize my RODI, which is all that I use for water changes. My tap is good, but I prefer the control that RODI water provides and would need to cut it anyway, to some degree. If you can do 50% water changes with RODI, I see no reason why you can’t move completely away from tap. When you say “dump in all 10 gallons of rodi first”, does that mean that it would be collected in a 10-gallon vat (which seems to contradict your “don’t have the space for a mixing vat” statement).
 
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So umm...I'm learning a lot which is great, but I feel my thread got derailed hard. @Deanna , have you done the whole remineralization thing, and if so, anything wrong/super bad with just adding water and then the minerals?
I apologize. Really yes, it is true, we had deviated a lot. But it is also true that the forum is more fun this way.
Getting back. I myself use RO in the water changes. I mix with the mains water and also add carbonates to raise the dKH. I don't need more salts because the water, in my Mediterranean town, has a TDS of 550. I mix a little of that water and that's it. I work in the aquarium with a TDS of 200, 4 dKH and PH 6.6, adding CO2. In short, everyone does what they can.
 

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Hi - I do a 70% water change with RODI. I put the water into the tank and then remineralize in the tank with dry salts. Never had an issue. That being said, I run with zero KH so I’m just adding GH along with other nutrients.
 
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