Chemistry guru wanted

[danmhippo]

OK, this is not the SW tank, but I figure some of you probably knows this anyway.

My tap water is pretty high in alkalinity, pH coming out of the tap is around 7.5. I have a planted FW tank that I want to bring the pH down to 6.5-6.8

Where I am at now, RODI unit is out of question. I want to know if I can soften my tank water using resin, would softwater translate into lower pH? I added a bag of water treatment resins for FW tanks last week. I put enough resin to treat 100G tank for 4 weeks (what it says on the label), and a week gone by, dkh has dropped a bit, but pH still stays at 7.5

I do not want to use peat in my tank as I will end up with tea-colored water. I also dose CO2 when the light is on (for the plants), it turns off when the light is off. I tested my pH (using hand held pH meter), the pH is unchanged day oir night. I've recalibrated the pH meter twice in a week already.

What else should I do to bring the pH down to 6.5?

 

[danmhippo]

BTW, my tank is only 10Gal.........

 

[Anonymous]

I suck at chemistry but back in the old days of running FW tanks I used a product called pHdown™ with no problems. Simply add to the water change water.
btw IBTM :wink:

Regards,
David Mohr

 

[danmhippo]

Yeah, I have been thinking about using pH down. But a bad habit (or good habit?) derived with years of keeping SW/Reef tanks is that unless I know what's in it, or how it works, I would hesitate using them in my tanks.

If pH down is effective, what does it do to water? Does it nutralize alkalinity? or is it simply stronger acid?

 

[Anonymous]

Yeah, I have been thinking about using pH down. But a bad habit (or good habit?) derived with years of keeping SW/Reef tanks is that unless I know what's in it, or how it works, I would hesitate using them in my tanks.

If pH down is effective, what does it do to water? Does it nutralize alkalinity? or is it simply stronger acid?

Don't know as I said I'm not a chemistry buff. :wink:
I did some homework for you though, it's contents is Sodium Bisulphate.
I used it when I was raising FW Stingrays (very sensitive to pH) and never had any problems that I was aware of because of it.

Regards,
David Mohr

 

[danmhippo]

Great! Thanks....

So the water softener resin that I bought is purely rubbish now? :x

 

[Anonymous]

not if you buy a water softener. :razz:

B

 

[Anonymous]

FWI
a pH of 7-7.5 is considered neutral.

 

[Anonymous]

Water softener does nothing to the pH.

 

[Anonymous]

You can still use the peat moss if you want it to soften naturally, just run activated carbon through it and it takes the tea color (tannins) out of the water but doesnt effect the PH. Used to have to do that for some Apistogrammas I was breeding a while back.

 

[danmhippo]

So....... Soft water brings the alk down, but does not necessarily lower the pH?

My head is spinning......kinda regret for flunking the chem back in the highschool.

 

[Anonymous]

See, Danm, pH is related to the concentration of OH- and H3O+ in the water, while water hardness/softness is related to other ions such as Ca/Mg etc.. Water softener resin only exchange a hard ion (Ca) with a soft ion (Na) and it does not affect the pH. However, DI resin exchange ion (both hard and soft) with a OH- or H3O+, so it will affect the pH. If I remember correctly, anionic DI resin will replace any negative ion with an OH-, and it will lower your pH. However, I don't recommand you to use it to lower your pH since it make your water chemistry wacko if you don't know what you are doing.

An alternative is to use organic acid or acid/buffer to lower the pH. This is how. pH Down and other pool product works. Same for peat moss, since it release organic acid to the water.

 

[danmhippo]

YAY! Thanks Reef Box! that cleared my head up a bit. So organic acid......vinegar works?

 

[Anonymous]

I would go with a buffering combo and use acetic acid (vinegar, if I remember correctly) and sodium acetate. The can be a better combo, depends on what pH you want to maintain, so you will need to verify a specific buffer with it buffering pH.

 

[mehdirah]

Hello,
I did that (acetic acid) once in a FW aquarium 20 years ago. And I can say one thing: NEVER do that!!!
I understood my mistake only when it was too late... OK, I explain.

it worked fine with the PH. But the problem is that acetic acid is a nutriment for bacteria. So, the next day morning, my aquarium was cloudy (I mean: 4 inches visibility), already 2 dead fishes. Just capture all the surviving ones (all at the surface gasping for oxygen), put them in a friend aquarium. And restart the aquarium from scratch...

I know now a bit more in water chemistry. To lower Ph, you must first lower PH buffering capacity of the water or you will need a lot of acid to lower PH. In practical, you must diminish the quantity of carbonate/bicarbonate ions=alkanility-->ions exchange resion (with capture both anions and cations to not desequilibrate water), RODI, rain water if you have it unpolluted,... And then you will be able to play with PH by small quantities of acid such as Ph minus (attention, if I remember well, it also contains phosphate, take care with algae), CO2 (probably the more natural way!). And do not lower alkanility too much as if buffering capacity disappear completely, ph may go far lower that what you intent.

Mehdi

 

[Anonymous]

mehdirah...nicely put!

 

[Anonymous]

Well, I am a chemist. I would advise leaving it alone. Why do you want the pH lower than 7.5?

 

[Anonymous]

Well, I am a chemist. I would advise leaving it alone. Why do you want the pH lower than 7.5?

Certain species of fish like the lower ph and will not spawn unless it's below 6.0 . Like these for instance...

 

[Anonymous]

You need to pick a buffer whose pKa is close to the desired pH. The pKa of bicarbonate/carbonic acid is 6.1. (carbonic acid forms when CO2 dissolves in water). You need both the acid as base components to make the buffer.

 

[danmhippo]

Scott, can you repeat that again in English for the someone that flunked chemistry back in highschool?