pH

[mudskipper123]

I am just a beginning hobbyist and I am having a hard time understanding what pH really is, can someone help?

[essabee]

pH is only the measurement of the ratio of H+ ion and OH- ion present in water. In neutral condition their numbers are equal and the pH is is at the middle of the scale of 14, that is at 7. Mathematical way of looking at it would be

[align=center](Number of H+ ion) divided by (Number of OH- ion)= 1 and the pH is 7[/align]


If the same formula gives an answer 10 then the pH would be 6 and acid
Again if the answer is 1/10 then the pH would be 8 and alkaline
If the same formula gives an answer 100 then the pH would be 5 and stronger acid
Again if the answer is 1/100 then the pH would be 9 and stronger alkaline

Each point on the scale follows this logarithmic 10 times position.

[Diana]

As regards to an aquarium:
Fish are better thought of in terms of what mineral level is optimum for them.

How pH happens in nature:
Rain has no excess of either H+ or OH-. It is neutral. It may pick up some carbon dioxide and (complex chemistry, never mind) become somewhat acidic.
Rain falls on rocks and soil. May seep in or run across the surface. Some rocks and soil dissolve quite easily, especially if the rain is a little bit acidic. The minerals in the rocks are often calcium carbonate and magnesium carbonate.
When carbonate is added to water it locks up the excess H+ and the water becomes more alkaline.

If we are talking about a part of the world that does not get much rain then there is not a lot of plant growth, and the minerals in the soil continue to dissolve. These minerals end up in the lakes and rivers. Then the water in the lakes evaporates, but leaves the minerals behind.
The lake water is very hard, lots of minerals, lots of carbonate. The pH is high.
The most common fishkeeping example is the Rift Lakes of Africa. Another example are the Caribbean Islands that some live bearers come from. An extreme example is the ocean.

If we are talking about a part of the world with high rainfall there are lots of plants. The rain may not fall on actual soil at all. Decomposing organic matter tends to have an acidifying reaction, so the rivers that run through rain forests (Amazon, Congo and others) tend to have very soft (no minerals) and acidic water.

Each lake or river might be a bit different, but overall:

Fish from rain forests thrive in soft, acidic water, often with organic acids in the water. They want low GH (General Hardness, a measure of calcium and magnesium) and low KH (Carbonates). pH is less important to fish, but low carbonates generally but not always means low pH. Neutral to acidic.
These fish have evolved to take advantage of every mineral that comes their way. When these fish are in water that is too hard they can accumulate minerals in their body and eventually die.

Fish from drier climates thrive in hard, alkaline water, usually with no organic acids. They want high GH and KH. The high KH almost always means high pH. They have evolved to get rid of excess minerals. When they are placed in water with too-few minerals their body is not very good at getting the minerals they need.

When I am setting up an aquarium with certain fish in mind I do this:
1) Make the GH right for the fish.
2) Make the KH roughly equal to the GH.
3) Ignore the pH.
4) Then I add to the filter some material that will help stabilize the water in the direction the fish like. Soft water fish = add peat moss. Hard water fish = add coral sand.
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In the early days of fish keeping, people barely even had pH tests, mostly it was litmus paper. You could tell 'acid' or 'alkaline' but there was no way to test for any of the minerals. People did not understand how the fish reacted with the water, especially the minerals in the water. All they could tell was 'the fish died' or 'the fish lived'.
Myths grew up about water changes, pH and related issues.
These myths have continued to this day, because the interaction of minerals in the water and fish seem too difficult to understand to some people. Sure it is a little bit harder than pH, but it is a whole lot more accurate!
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FISH DO NOT CARE ABOUT THE pH.
The best way to test this is to alter the pH without changing the mineral levels. One way to do this is to add CO2.
As long as you do not add a toxic amount, you can add it as fast as you want, thus changing the pH really fast. Most fish are fine with this.
The opposite test is one that all too many fish keepers do inadvertently. Take new fish home from the store and put them in a tank with mineral levels that are different from what they were used to at the store. This is the problem of acclimating the fish. There are ways to do this right, but do not put fish in water that is harder or softer than what they are used to. Do not do water changes with water that is too different.

[mudskipper123]

So pH is different from place to place depending on the minerals that are in the rocks and sediment?

[essabee]

So pH is different from place to place depending on the minerals that are in the rocks and sediment?

Not only at place to place; but it varies with seasons too at the same spot; as does GH and KH. So every fish be it from soft acidic water areas or hard alkaline areas have learned to adapt to a range of pH, GH, and KH. Not even the oceans have a homogeneous pH, GH, or KH all over or invariable with time.

SO - unless you are keeping fishes that are from very isolated niche - don't worry too much about all these factors and just know what your water supply is (same or not for the general area). If it is generally the same for the region then stick to fishes bred locally as these fishes are adapted to your conditions.

The pH, GH and KH just should not be too extreme to escape the range the fish has adaptation for.

[Dutchman]

Just my . . .

There are however some practical reasons why you should keep the pH below 8.

Above pH 8, ammonia can only exist in its unionised form, ie: NH3 which is extremely toxic to fish (fish urine is pure ammonia). Also CO2 is not freely available to the plant. At those levels the gas is bound into carbonates and hydro-carbonates.

I know that a lot of tap water in the US comes from wells with a pH above 8, in which case you would be well advised to lower the pH with a bit of lemon juice or white vinegar and get it to about 7.5. (prepare the water in a seperate container first)

[Diana]

Mudskipper123, what sorts of fish are you thinking of keeping?

[mudskipper123]

I already have fish and not planning on getting any more, I was just trying to understand the chemistry that occurs in the aquarium.

[discus21473@aol.com]

[quote="mudskipper123"]I am just a beginning hobbyist and I am having a hard time understanding what pH really is, can someone help? [/quote

Water is what water flows thru world round, pH is short for parts hydrogen + - within the water, GH stands for general hardness and KH is carbonate hardness. pH is measured on a scale of 0 to 14 with 7 being neutral neither acidic nor basic
Gh and KH is the water hardness, Hardness scale for aquarium water is
0-2 dH= Ultra-softwater
3-8 dH=Softwater
9-15 dH=Moderately hard water
15-20 dH= Hard water
>20= Very hard water
Each degree of hardness (dH) is equal to 30 milligrams of calcium carbonate per liter of water. This can be expressed as parts per million (ppm). Therefor, one degree of hardness is equal to 30 ppm of hardness.
water with a pH of 6 is 10 times more acidic than water with a pH of 7. Various species of fish have adapted to water that has differant pH levels. Most fish do not tolerate a pH reading outside their preferred range, nor do they adapt well to rapid changes in pH. Without exception, marine organisms do best at a pH of 8.0 to 8.3, similar to that of the ocean itself. Freshwater fish vary more in their pH preferences. Soft water fish from South American and African rain forests do best in water that has a pH 5.0 to 6.5. Cichlids from the Rift Lakes in Africa do best if given alkaline conditions at a pH range of 7.8 to 8.2. Most other freshwaer species do well at a neutral pH 6.5 to 7.5
dissolved solids, Different aquatics environments around the world also have varing amounts of dissolved minerals in them, generically termed dissolved solids. The nature of these dissolved solids vary with the region. In many cases the material is calcium or magnesium carbonate. If water contains a relatively large amount of disso;ved solids, it is called Hard. These calcium compounds act as a buffer in the water, resisting any changes in pH and keeping bthe water at an alkaline level. Water with fewer dissolved minerals in it is called Soft. The scale most often used is dH, or degrees of hardness.
Good luck with your new adventure into aquatics may it be a good one if you have problems don't be afraid to ask we all here will help anyway we can GOOD LUCK

[Diana]

Therefor, one degree of hardness is equal to 30 ppm of hardness

1 German degree of hardness (The most common way of measuring hardness in aquariums) = 17.9 ppm of hardness. The ppm reading is common on some testing supplies, for example the dip-stick type made by Jungle and some others.

These calcium compounds act as a buffer in the water, resisting any changes in pH

Carbonates are the buffer in this example. There is an interaction between carbon dioxide, carbonates, bicarbonates and the hydrogen in the water. When there are a lot of carbonates or bicarbonates present they remove the extra hydrogen and the water becomes less acidic.
Does not matter how much calcium is in there. If there is no calcium in the water and you add bicarbonate (for example baking soda) the water becomes more alkaline.

Most of the common TDS (Total Dissolved Solids) meters in the hobby are testing conductivity, and relate that to water that has only NaCl dissolved in it. So my TDS meter might read 300 ppm. What it means is that my water has the same conductivity as water that has 300 ppm of ions from NaCl. This is not a reading of either GH or KH, nor is reported in degrees of hardness.

You can report General Hardness in degrees and use the abbreviation dGH, degrees of GH.
You can report Carbonate Hardness in degrees and use the abbreviation dKH, degrees of KH.