Chemistry experiment!

[adeebm]

Well, I had bottles of seachm acid buffer, alkaline buffer, and equillibrium sitting around from ages ago. So I thought I'd put them to use in my to be RCS tank. Usually, messing with RO water would be a pain, but I figured in a small tank it won't be much of a problem. Anyway, with these three products and RO/DI water, I should be able to choose the exact pH, GH, and KH values I want, more or less. Or so seachem claims. I haven't heard too much about how well it works, so I'm about to find out. I'm going to aim for a GH of 8, KH of 6, and pH of 7, which should be more or less ideal for RCS.

Time to get out my scale, since I'll be measuring down to .25 grams! I sure do love chemistry

--Adeeb

 

[ColtsGuy77]

Thats really interesting

 

[Wy Renegade]

Curious, so following along. Are you using this for top off water, or setting the tank up this way?

 

[adeebm]

I will be testing it out with 5 or 10 gallons of water. If it works as expected, then I will set the tank up with it. It's really the same concept as using marine salt in SW, just a bit more measuring.

--Adeeb

 

[Wy Renegade]

Interesting, what about trace elements like strontium and iodine?

 

[aqua_chem]

Henderson–Hasselbalch is your friend.


Do you know what buffers the seachem products use?

 

[adeebm]

I'd have to get back to you on the exact composition since im on my phone. It's not phosphate based though. Probably a carbonate/bicarbonate system. As far as trace elements, equilibrium contains the major elements, as it is meant for replenishing RO. I don't know that iodine and strontium are too important in FW. I'll have to look at the complete list. There's always the food as a source of trace elements too.

--Adeeb

 

[adeebm]

Henderson–Hasselbalch is your friend.

Ah yes, I had good times with that equation in chem class. Got me the highest score in a titration lab.

For trace elements, it seems the minor trace elements are not included. I don't know how large of a role they play in fish health, but I do have a bottle of some kent discus trace stuff lying around. From what I've heard, trace element supplements are little more than water, but it can't hurt.

As far as composition alkaline buffer gives no ingredients list, so I can only assume it is some combination of carbonates. Acid buffer says it contains bisulfate salts, which makes sense considering it buffers pH to an acidic level(~6).

I'm going to add the stuff now and let it mix overnight.

--Adeeb

 

[Wy Renegade]

For trace elements, it seems the minor trace elements are not included. I don't know how large of a role they play in fish health, but I do have a bottle of some kent discus trace stuff lying around. From what I've heard, trace element supplements are little more than water, but it can't hurt.

--Adeeb

Opps! Sorry my bad, I thought we were talking about a saltwater tank rather than freshwater. I'm sure there probably are trace elements in freshwater as well, although I'm not familiar with exactly what those might be. Curious also to see long term how it does. Does this mixture somehow include normal salt?

 

[adeebm]

Yikes, something went wrong... TDS came up at 548ppm, and even my tap is only 250ppm lol.

KH-8
GH-15
pH-8.2

Not exactly what I was aiming for... I have 3 guesses as to what went wrong. Either I calculated wrong, my scale isn't is accurate as I thought, or there was contamination. I mixed the water in a bucket I usually use to mix SW. I had washed the bucket before mixing, but it's possible some of the residual salt stayed in the bucket, and on the powerhead.

Seeing as the TDS is off the charts, I would assume it was the bucket. I guess I'll be needing another one now.

--Adeeb

 

[adeebm]

Well, after more research, I'm confused as to seachem's claims about their product. Assuming it's a carbonate buffer, it follows the equation CO2 = 3 * KH * 10(7-pH) roughly. Seachem seems to claim that you can choose any KH and pH and set them proportionally, yet that shouldn't be true. Unless they have some sort of magic buffer, pH will be proportional to KH and dissolved CO2 levels(about 1-4ppm ambient). By the above equation, my ambient CO2 levels are about 1.5ppm. Thus, in order to have a pH of 7, my KH would have to be .5 which seems to be a bit illogical.

Also, assuming KH was .5, and was the only buffer in use, it would mean the pH is very unstable, and that biological processes in a tank would cause pH swings. Yet many members here naturally have tap water with a pH of 7 or less, but with a higher KH and no swings? I thought carbonates/bicarbonates were prevalent in freshwater, so how is this possible? I must be missing something here...

--Adeeb

 

[aqua_chem]

Well, after more research, I'm confused as to seachem's claims about their product. Assuming it's a carbonate buffer, it follows the equation CO2 = 3 * KH * 10(7-pH) roughly. Seachem seems to claim that you can choose any KH and pH and set them proportionally, yet that shouldn't be true. Unless they have some sort of magic buffer, pH will be proportional to KH and dissolved CO2 levels(about 1-4ppm ambient). By the above equation, my ambient CO2 levels are about 1.5ppm. Thus, in order to have a pH of 7, my KH would have to be .5 which seems to be a bit illogical.

Also, assuming KH was .5, and was the only buffer in use, it would mean the pH is very unstable, and that biological processes in a tank would cause pH swings. Yet many members here naturally have tap water with a pH of 7 or less, but with a higher KH and no swings? I thought carbonates/bicarbonates were prevalent in freshwater, so how is this possible? I must be missing something here...

--Adeeb

That equation, flawed as it may be, uses a fundamental assumption that the carbonic acid-bicarbonate-carbonate buffer system is the only buffer system present in solution. Adding your own buffer significantly alters these conditions, rendering the equation utterly useless.

 

[adeebm]

Yes, it is an extremely simplified equation used to calculate CO2 levels on aquaria. I didn't feel like going through the full equations. Like you said, it is useless for a non carbonate buffer, but isn't that the prevalent buffer in most home aquaria?

--Adeeb

 

[aqua_chem]

1) I'm pretty sure that equation is pretty useless regardless
2) Assuming it's a carbonate buffer. Seeming like a pretty big assumption at the moment.

I've never been properly motivated to look at that equation myself, but it's come up several times now on these forums. I suspect that it's not what it's cracked up to be.

 

[aqua_chem]

Just a quick addition. I ran the numbers myself and came up with (about) the same thing, except with 2.94 instead of 3. So it stands up on a purely theoretical a basis.

 

[skiweeangel]

Henderson–Hasselbalch is your friend.


Do you know what buffers the seachem products use?

Makes me smile!

 

[adeebm]

Got a clean bucket, and I'm gonna rinse out the powerhead and try again tonight. This time I'll use seachem's exact ratios, and won't add equilibrium until later. If this doesn't work then I'm gonna have to say that these products are faulty, which would be a shame because seachem makes some great stuff.

--Adeeb

 

[MonsterfishGuy]

Lol

Make your own opinion everyone!! Interesting experiment but that doesnt prove the product does'nt do whats claim about it!!!!

If you study science then you know that ASSUMING its a carbonate mix is hypothetical, look if the Pk is on the label... And try to figure the quantity of bi-carbonate, carbonate and borate is almost impossible!!

Plus telling that if YOU are unable to find the exact formulation by testing with color-comparison test (instead of titring) without the original formula of the product made by A DOCTOR in chemistry is very pretentious!!! Except if you are a doctor too!

Those product are done after several reserch done in aquarium containing life, the only big companie that does it with lots of precision and passion!!

Other dont test in aquarium, they assume what the manufacturer of their product says ( manufacturer that give you product without testing in aquarium assuming that regular test on pure water are enough to know what they do when there is life interacting. )

Plus they dont tell on those bottle, what a dose is suppose to give as a result, they just say they are the most concentrated and say test after 24 hours to make sure your ok. With the result you show, its well concentrated.

Finally, its just impossible to know whats in there without testing fusion point, and then try to balance the equation with the element you found and their respective Pk. Dont take your result to seriously!!

For those who read, if you cant do you precise experiment with real lab test, then take those result lightly and not as a 100% sure and prooved info, its opinion!!

Make your own oponion dont let people do it for you!!

As for the experiment, give your exact protocol so someone else can do the experiment with the same result, thats the only way you can tell your experiment is precise!!

Good luck!

 

[MonsterfishGuy]

They did serious reserch for the last 30 years with doctors in chemistry, biology bio-chemistry!!

I assume that this are the best product you can have in all aquatic manufacturers!

But its an opinion too!

 

[adeebm]

Not sure what your trying to say there. The bottle doesn't list a pKa value or any ingredients or I would have posted them. Anyway, the experiment is simple: follow seachem's directions listed on the bottle with RO water. If it doesn't work as expected, either the directions or the product is faulty. Just because it's a reputable company doesn't mean they can't have bad products. I'm not saying it is faulty yet, I haven't tried.

--Adeeb