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Hello Aquapons, My GH is off the scale. My PH is holding at 7.6 to 7.8 Cant seem to move it lower with acid. Using Nylons with peat to try and help. Any Ideas. The KH is at 125ppm as well.

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Sorry David, what do you mean by "GH" and "KH"?

how old is your system?  PH shold start going down on its own with age.  what is your alkinlinity?

How many gallons?  what is your water source? how much you adding every week, what plants are you growing ideal fish PH is 7.5

Ok, general hardness and kinetic hardness.  Well, if your water is to hard coming in, you might look into RO.  There's a lot of small cheap systems now. (I was looking at one around $200).  It's not like you'll be using lots of water. . .

Time!!!!  Give it time.


If you can start collecting some rain water for some of your top ups you will have less issue with bumping your pH up by adding well or city water.  I get my water from a limestone aquifer when natural rain isn't topping up the system on it's own.  The well water will bring my pH up.  But the natural action of the bacteria working the nitrogen cycle will use up some of that hardness and bring the pH down in time if you are not having to add too much of that really hard top up water.


A starting pH between 7.6 and 7.8 is fine.  Just cycle the system up and keep an eye on the pH over time.  I noticed that as long as you don't have a strong buffer mixed into your media, there is a good chance at about the time the nitrite spike from fishless cycling drops, so could the pH.  Don't let the pH drop too far since if it gets too much below 6 you could stall or even kill off your bacteria.

Thank gents on the info. We get less than 7 inches of rain so catch basin is out of the question. I will look into a RO as an option. My water starts at 8.2 to 8.4. I was able to move it about 08 with acid then hit the buffering wall. Checked my hardness and it was off the chart high so I realized why I couldnt move the ph anymore. Will look at alternate source from a RO. Nevada is dry and the moisture flys out of the plant here so a good souce of aqua will be a big help. Not as the primary but just to temper the hardness.
"Checked my hardness and it was off the chart high" What is the number....RO proabably a no go.  Tradtional hydroponics clean water "aqauaponics dirty" UVI... you also should get your water completly tested at a lab to start so know exactly what you are starting with.  Which acid did you lower with?  Please very detailed information....Do not give up rain water and or a truck from spring source may be a option if your starting water is no go
to go with JR's comments.  You might also put a barrel of your top up water with an aerator to do some pH adjustment experiments that are not connected to the AP system.  Being able to work on pH in a measured container of water that is not being affected by all the other processes in the AP system could allow you to figure out how much acid dosing it takes to adjust a measured amount of your top up water into a comfortable range.  (This is likely to take several doses over a period of time since there is likely to be some bouncing as the acid is added and then the pH comes back up as the buffer is dissolved until eventually you find out how much it takes.)
Jr I think getting my water tested is a good Idea. I know it is full of Iron and minerals. As far as me trucking water in no thanks to much hassle. I'll buy a RO.. I am using muratic but have backed off for about 2 weeks since my PH is tolerable and the acid was having no affect. I have added 3 gal to my system of 1600 gal so far. As far as the exact GH the little test kit maxed out at 225 ppm at 12 drops and I didnt even get a color change at 12 drops. So very hard, Probable would make your sticker peck up ahah. I know the aquaponic process will lower ph over time not sure of GH. Just trying to stay ahead of it. TC I will fill a 5 gal bucket and see how much acid it takes to move it to 7.0 I did add 20 ounces every 3 days to get to this level and it is stable due to my high KH , just got nervous about so much acid. , Thanks for the help gents. D


I experienced some of the same problems you have described.  My tap water is around 9 pH, 12 grains on the hardness scale.  I was using muratic acid to regulate and pH would change slightly and then all of a sudden I would have a drastic swing in pH.  I killed some fish this way even though I was treating a bucket at a time and testing everything before adding to system.  I had a hard time finding the right combination.   I purchased a bottle of pH down (phosphoric acid?) and tested in a five gallon bucket.  I found that if I draw a 5 gallon bucket and let it sit(to room temp, 56 degrees) then add 1 Tbs. of pH down the water is 7.5 every time.  I usually let this sit for another day and check again before adding to system.  When I move the system outdoors again I will go through the process again to find out if/how the warmer temps affect it.  The system has been humming along with no hiccups(knock on wood) for around three months now since I switched. 

.Interesting maybe I should switch to phosphoric and try to move the GH and ph that way. Hmmmmmmmmm. Will probably let it ride because I have 60 little fingerlings and they seem to be doing great and water quality is great right now. Will move all the water I add to system to 7.0 in a separate bucket with phosphoric.

If your source water is above pH 8.0.... then your source water is carbonate buffered... usually from limestone aquifers...


Trying to treat a large volume of water in your fish tank with acid will just see your pH bounce back to the previous value... until the carbonate buffer has been exhausted....


Not good for your fish...


Topping up your tank with the same source water will just add more carbonate buffer to your system...


If you have fish in your system... then treat your top up water (a lesser volume)... as "K edmonds" is doing... then add to your tank...


Over time the pH... along with the nitrification trend to acidicy.... will lower the pH....


You can if you wish also additionally treat the fish tank itself... but only with minor amounts of acid... so as to not shock the fish with pH bounce... just don't be surprised if the pH returns to previous value... it will... until the buffer is exhausted...


Preferably... use Hydrochloric acid... muriatic acid... rather than phosphoric and/or other "pH down" products...


It's cheaper... and more effective...

The above will lower your carbonate hardness (kH)... not necessarily your general hardness (gH)... which is more a measure of the combined magnesium, calcium and other metalic ions present in your water... what's often referred to as "hard water"...


A general technical explaination...


There are two types of water hardness: general hardness (GH) and carbonate hardness (KH).  A third term commonly used is total hardness which is a combination of GH and KH. 


Since it is important to know both the GH and KH, the use of total hardness can bemisleading and should be avoided.


General hardness is primarily the measure of calcium (Ca++) and magnesium (Mg++) ions in the water.  Other ions can contribute to GH but their effects are usually insignificant and the other ions are difficult to measure.  GH will not directly affect pH although "hard" water is generally alkaline due to some interaction of GH and KH.

GH is commonly expressed in parts per million (ppm) of calcium carbonate (CaCO3), degrees hardness (dH) or, more properly, the molar concentration of CaCO3.  One German degree hardness (dH) is 10 mg of calcium oxide (CaO) per liter.  In the U.S., hardness is usually measured in ppm of CaCO3.  A German dH is 17.8 ppm CaCO3.  A molar concentration of 1 milliequivalent per liter (mEq/l) = 2.8 dH = 50 ppm. 


Note that most test kits give the hardness in units of CaCO3; this means the hardness is equivalent to that much CaCO3 in water but does not mean it actually came from CaCO3. 


Water hardness follows these guidelines:

      0 -  4 dH,    0 -   70 ppm : very soft
      4 -  8 dH,   70 -  140 ppm : soft
      8 - 12 dH,  140 -  210 ppm : medium hard
     12 - 18 dH,  210 -  320 ppm : fairly hard
     18 - 30 dH,  320 -  530 ppm : hard
     higher : liquid rock (Lake Malawi and Los Angeles, CA)

General hardness is the more important of the two in biological processes.  When a fish or plant is said to prefer "hard" or "soft" water, this is referring to GH.  Incorrect GH will affect the transfer of nutrients (trace elements) and waste products through cell membranes and in AP systems...



Carbonate hardness (KH) is the measure of bicarbonate (HCO3-) and carbonate (CO3--) ions in the water.  In freshwater aquariums or aquaponic systems of neutral pH, bicarbonate ionsv often predominate.


Alkalinity is the measure of the total acid binding capacity (all the anions which can bind with free H+) but is comprised mostly of carbonate hardness in freshwater systems. 


Thus, in practical freshwater usage, the terms carboante hardness, acid binding, acid buffering capacity and alkalinity are used interchangeably.  In an aquarium, or aquaponis system, KH acts as a chemical buffering agent, helping to stabilize pH.  KH is generaly referred to in degrees hardness and is expressed in CaCO3 equivalents just like GH.

In simple terms, pH is determined by the negative log of the concentration of free hydrogen ions (H+) in the water.  If you add a strong acid such as hydrochloric, or nitric acid to water, it completely dissociates into hydrogen ions (H+) and its "conjugate base" or "salt".


The hydrogen ions freed in the reaction then increase the concentration of hydrogen ions and reduce the pH.  Since nitric acid is the end product of the nitrogen cycle, this explains why aquarium pH tends to decrease and nitrates tend to increase over time.

When the aquarium has some carbonate buffering in it, the bicarbonate ions will combine with the excess hydrogen ions to form carbonic acid (H2CO3) which then slowly breaks down into CO2 and water. 


Since the excess hydrogen ions are used in the reaction, the pH does not change very much.  Over time, as the carbonate ions are used up, the buffering capacity will drop and larger pH changes will be noted.

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