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[–]Indemnity4Materials 96 points97 points  (12 children)

Degassing water typically results in a pH rise of 1-1.5 pH units.

Carbon dioxide in the air will diffuse into water. It forms an equilibrium of CO2 gas, dissolved or aqueous CO2 and a bunch of carbonate/mineral carbon species.

Boiling on the stove is a really slow process. By heating the water you shift the equilibrium so any mineral carbonates convert back to CO2, but then the water bubbles, it turns over from bottom to top, steam is moving away from the water carries away other gases too - all of this causes any dissolved CO2 to boil away.

Microwave heating is poor at degassing. The heating is really fast but it's not enough time, the water is not turning over and you aren't generating enough steam to push away any gaseous CO2. You've probably seen the effect where you heat water in the microwave then accidentally shake the cup or add in some solid - poof, steam explosion. Most of the CO2 will remain in the water.

[–]Bohrealis 12 points13 points  (4 children)

I just want to point out that this *should only work for acidic pHs. It would explain the difference between measuring 6 and 7, but theoretically not 7 and 8. However, I doubt an aquarium pH meter is that accurate or regularly calibrated.

[–]Melodic_Currency_822[S] 7 points8 points  (3 children)

Universal indicator strips

[–]redligand 24 points25 points  (0 children)

These aren't massively accurate either and their interpretation is somewhat subjective.

[–]Bohrealis 6 points7 points  (1 child)

Oh okay. Next thought: tap water was used? It's probably the same explanation but the water was a little hard. Hard water is slightly basic, which was balanced out by CO2. So when you removed CO2, instead of going from acidic to neutral, it went from neutral to slightly basic. You could check by redoing the experiment with distilled water.

[–]Melodic_Currency_822[S] 2 points3 points  (0 children)

Interesting. I looked it up and apparently the water here normally has a pH of about 7.5. Will try with distilled water

[–]Born-Sheepherder-692 2 points3 points  (6 children)

This makes sense!

[–]jeisan0283 2 points3 points  (5 children)

Water chemist here. Tap water usually is treated with monochloramine as a disinfectant, ( free chlorine and ammonia) which likes to be most stable in drinking water between pH 7.5 and 8. That may also explain the slightly elevated pH followed by the degassing of CO2.

[–]Born-Sheepherder-692 0 points1 point  (2 children)

That makes sense too! Can fish live in D.I. Water?? Probably lol😂 Is D.I. Water free of those chemicals?

[–]jeisan0283 1 point2 points  (0 children)

I used RO and DI all the time for my tank, but made sure to add nutrients for the plants. Lol

[–]BioTechproject 1 point2 points  (0 children)

Technically lots of freshwater species can, as minerals usually leech out of their own bodies and the surrounding materials. However it makes sense to remineralize, to add nutrients and keeping the water more stable.

[–]midnight-cheeseaterOrganometallic 0 points1 point  (1 child)

Do they really add both chlorine and ammonia at the water treatment plant? I thought they only added small amounts of chlorine, and that chloramines were formed by oxidation of dissolved nitrogenous organic matter in the water.

[–]jeisan0283 0 points1 point  (0 children)

Yes, it's a combo of both. At stations you can also have ammonia boost tanks. Out in the field you want to prevent monochloramine from becoming dichloramine, then after trichloramine you get free chlorine that causes disinfection byproducts like THMs and HaloAcetic Acids. So to counteract, add more ammonia and it will shift the equilibrium back to mono. But too much ammonia/organics will lead to higher nitrification.

[–]Patrick26 5 points6 points  (10 children)

Dissolved CO2, maybe, being lost in the pot.

[–]BioTechproject 1 point2 points  (5 children)

Question: what did your friend think the point was in heating it?

[–]Melodic_Currency_822[S] 0 points1 point  (4 children)

Getting rid of chlorine

[–]BioTechproject 2 points3 points  (0 children)

Yeah in that case the boiling method would work best. You'd get rid of chlorine and chloramines/ammonia. As, like stated by others, degassing doesn't work well when microwaved.

[–]Sybekhide 0 points1 point  (2 children)

There are way better methods to achieve this. Just buy a cheap water dechlorinator in a bottle. About 3$

[–]Melodic_Currency_822[S] 0 points1 point  (0 children)

Yup I know, but I'm asking about why the pH changed

[–]BioTechproject 0 points1 point  (0 children)

On the other hand that can release ammonia from chloramines. It's better to just airate it with an airpump or sth over night.

Also water conditioners are still necessary to chelate any heavy metals present

[–]SaltSlanger 2 points3 points  (0 children)

Wild guess, but I imagine boiling evaporates more water than microwaving thus concentrating the basic mineral salts in the water. I reckon its more because of the concentration of the aforementioned salts that causes it to be more alkaline rather than the material of the vessel.

[–]oldmanartie 0 points1 point  (4 children)

Unless you’re in a mad rush you can just leave water sit out overnight and the chlorine will dissipate. You’ll want to use a conditioner with EDTA with every water change regardless to bind up any metals that will be harmful to fish. Most of these products also have thiosulfate or other chemicals to neutralize any residual chlorine as well.

[–]piyrwq 1 point2 points  (0 children)

Yes. Or just aerate for an hour to drive off the chlorine. Boiling saves no time as it needs re-aeration after boiling anyways. The fish need atmosphere-equilibrated water to get the right levels of O2 and CO2.

[–]BioTechproject 0 points1 point  (2 children)

EDTA is most common as it's very cheap, I'd suggest using ones that are less bioaccumulative. Aka: make the investment of getting higher quality water conditioner

[–]jeisan0283 0 points1 point  (1 child)

I thought EDTA just chelates inorganics for removal, but the real money saver is sodium thiosulfate. Actually I love sodium borohydride, but I'm afraid of what it would do to fish. I'll keep that strictly to my CN analysis.

[–]BioTechproject 0 points1 point  (0 children)

It does. But that comes with its own problems. So the first thing is that it can't be broken down by organisms and is also rather UV resistant. So it can 1. have some unforseen effects on organisms and 2. does annoying stuff, like encapsulating minerals making them harder to take in by organisms, like e.g. iron as they now have to work harder to rip it out of that chelated complex again or can 3. dissolve minerals, leading to them being swept away or 4. dissolving harmful metals, like lead and spreading those around and so on. It's a real pain.

The only upside is that it's cheap af and yet very strong [depending on mineral and may not even be a pro depending on what you want] compared to other chelating agents.

I have the luxury of not having chlorine and chloramines in my tap water, but shouldn't simple air pump airation over might be enough to get rid of them? It's not like there's a lot of it in there, just a few milligrams afaik

[–]tlyons2230 0 points1 point  (0 children)

So this explains why making yes from a kettle is better than from a microwave?