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The difference between alkalinity and pH?
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Author:  Harmony Brook [ Mar 1st, '13, 08:22 ]
Post subject:  The difference between alkalinity and pH?
First, I am new to this...so please bear with me.

I always thought that alkalinity was synonymous with a high pH, but I have had a hard time keeping my pH low...My test strips show a pH of about 8 and an alkaline level of of over 300 ppm.

I read in Sylvia Bernstein book that a high alkaline level could "effect the buffering capacity" of the water.

So it seems that lowering my pH is NOT the same as lowering my alkalinity, and I need to get that lower, but most of the time I try to look up how to do that...it starts talking about lowering the pH.

P.S. I am using General Hydroponics pH down product, and I live in the Rocky Mountains so all of our water has high alkalinity!
Author:  Charlie [ Mar 1st, '13, 08:32 ]
Post subject:  Re: The difference between alkalinity and pH?
I believe Carbonate hardness is usually related to alkalinity
Author:  RupertofOZ [ Mar 1st, '13, 08:51 ]
Post subject:  Re: The difference between alkalinity and pH?
Harmony Brook wrote:
First, I am new to this...so please bear with me.

I always thought that alkalinity was synonymous with a high pH, but I have had a hard time keeping my pH low...My test strips show a pH of about 8 and an alkaline level of of over 300 ppm.

I read in Sylvia Bernstein book that a high alkaline level could "effect the buffering capacity" of the water.

So it seems that lowering my pH is NOT the same as lowering my alkalinity, and I need to get that lower, but most of the time I try to look up how to do that...it starts talking about lowering the pH.

P.S. I am using General Hydroponics pH down product, and I live in the Rocky Mountains so all of our water has high alkalinity!

Charlie is right... alkalinity is measured as the degree of "carbonate hardness".. in your case 300ppm...

It can be thought of as the amount of carbonate buffer... that keeps pH high...

And your pH wont fall... as long as you have a large degree of carbonate hardness....

Sylvia's comment that "that a high alkaline level could "effect the buffering capacity" of the water" is kind of right... but not really perhaps understood... or expressed correctly...

The "high alkaline level" isn't "effecting" the "buffering capacity of the water".... the buffering capacity of the water... is completely due to the carbonate hardness... the alkalinty... and reflected in the pH...

Until the alkalinity is consumed... the pH will not fall....

The only way to consume the carbonate hardness.... is through the acidification due to nitrification... over time...

Or by the addition of acid... perferably Hydrochloric acid (muriatic acid)...

Howevr if your source water... that you will inevitably used for top ups to your system... has a high carbonate hardness.... ever top up addition will just be adding back carbonate hardness to your system... probably as much as has been consumed...

Taking into account the amount of acid that would be required to consume the carbonate hardness... thus reducing pH... in the large volume of water in the fish tank... and the requirement of keeping pH changes within a minimal range.. for the sake of fish health....

Treating your fish tank.. with acid.. to lower the alkalinity/pH.... is somewhat of a futile exercise... if you add untreated source water high in carbonate buffer... back to the system... through top ups...

Treat your source water... before addition to the system.... with Hydrochloric acid... to adjust the pH to 6.0....

And over time... with the natural acidification through nitrification... your pH will drop (as your "alkalinity" falls)...

Be patient... it wont happen overnight.... but it will happen...

Of course... once your "alkalinity" is consumed.... your pH will begin to fall increasingly rapidly....

And then you'll actually have to add some alkalinity back into your system.... :D
Author:  blind freddie [ Mar 1st, '13, 16:51 ]
Post subject:  Re: The difference between alkalinity and pH?
Thanks a million Rupert, Ive been trying to reconcile the alkalinity/pH equasion in my mixed up head for a while.

I learnt what to, and when to do it, but my understanding of why? was cloudy (I have those days)

Cheers BF
Author:  Harmony Brook [ Mar 5th, '13, 01:14 ]
Post subject:  Re: The difference between alkalinity and pH?
Thanks for the information.

After getting some of this info, and knowing that adding acid was probably the only reasonable way to overcome such a high alkalinity, I did a couple of different things this weekend:

1st, I replaced about half of my water with distilled water from a culligan's machine (3 dollars for 10 gallons). My hope was to lower the alkalinity enough that I could use less acid...and perhaps be a bit easier on my fish.

It worked pretty well...my ppm went from over 300 to somewhere around 150, and my pH went down for the first time.

There was a side effect though, the ammonia and nitrite levels spiked to very dangerous levels...I wonder if the high hardness of the water was also buffering the N levels?

I am torn now since I dont want to keep adding distilled water, but with ammonia levels this high, the normal solution is to do water changes, right?

Is that common? I went from having a pretty stable system with a high pH to a really volatile system and I am hoping it will equalize eventually....though I am not sure I have discovered a sustainable solution. I knew I was going to have trouble with the local water, but diluting it with distilled water cant be the answer if I move to a much larger system!
Author:  RupertofOZ [ Mar 5th, '13, 02:41 ]
Post subject:  Re: The difference between alkalinity and pH?
There's no reason for ammonia & nitrite levels to spike because you lowered the "alkalinity"... and pH of the system... if it was indeed actually "stable".... (unless you dropped the pH below 6.0)...

Generally.. for the same water temperature... the lower the pH... the higher the safe level of ammonia toxicity...

More info please... start/end pH... start/endwater temperatures.. method of oxygenation... number of fish... increased feeding???
Author:  Harmony Brook [ Mar 5th, '13, 02:59 ]
Post subject:  Re: The difference between alkalinity and pH?
RupertofOZ wrote:
There's no reason for ammonia & nitrite levels to spike because you lowered the "alkalinity"... and pH of the system... if it was indeed actually "stable".... (unless you dropped the pH below 6.0)...

Generally.. for the same water temperature... the lower the pH... the higher the safe level of ammonia toxicity...

More info please... start/end pH... start/endwater temperatures.. method of oxygenation... number of fish... increased feeding???



The ammonia & nitrite levels were all super low (generally not even registering on my test strips) for 3 weeks straight.
Alkalinity was well over 300 ppm for all three weeks.
pH was between 8.1 to 8.4 the for all three weeks (I kept adding acid, but it never seemed to overcome the alkalinity because of the hardness of the water)
Temp was cool room temp, but I didnt measure that consistently.

After changing out a lot of the water with distilled water:
Ammonia and nitrite levels are all in my test strip graphs show "danger" levels.
Alkalinity was between 150-300.
pH is still fluctuating a bit, but about 7.9 right now...I have been slow in adjusting that for my fish's sake.
Temp is the same.

I have 8 little goldfish in 15-20 gallons of water.

Oh ya, and I run the pump for 30 min per hour. The drain drops the water about 6 inches back into the fish tank dragging bubbles down with it. There are a couple of other little water flow sections from the pump back flowing into the fish tank and the pump into the grow media...that is all the oxygenation that I am currently doing.
Author:  solidwoods [ Apr 9th, '13, 22:09 ]
Post subject:  Re: The difference between alkalinity and pH?
If Harmony Brook used rain water for water topoff what effects would that have?
Thanks
jim
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