Tropical Fish Keeping - Aquarium fish care and resources

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pop 07-10-2014 04:09 PM

ramble into power of Hydrogen
 
A ramble into power of Hydrogen
When I started keeping fish I thought how hard can it be? You just add water, livestock and food then enjoy the benefits of my labor. How foolish new fish keepers are I quickly learned about pH and thought it’s not rocket science it is either acid or alkaline how hard can that be. This is a common mis-understanding of pH. I soon learned that I always had the terms confused it is not alkaline but basic, Yes acid or basic where did I get the notion alkalinity; since then I have learned that alkaline referees to the stabilization of pH via carbonate and general hardness.

What is pH? To begin the lower case p and capital H represents percent hydrogen or more correctly power of Hydrogen. The power of hydrogen is the balance between positive hydrogen ion (H+) and the negative Hydroxide ion (OH-). When the amount of Hydrogen (H+) ions are exactly matched to the hydroxide (OH-) ions the solution is neutral. When there are more Hydrogen ions (H+) than hydroxide ions (OH-) the solution is acid and of course when there a more hydroxide ions (OH-) than Hydrogen ions (H+) the solution is basic.

What is the difference in the nomenclature of the pH scale? Integer difference is tenfold so that a pH of 7.0 is 10 times more acid that a pH of 8.0 and the pH of 9.0 is 100 times more basic than pH of 7.0. Integer shifts represent giant changes in the relationship between Hydrogen (H+) and hydroxide (OH-) ions. The impact of partial changes in pH represent a smaller change in the Hydrogen / hydroxide relationship so a pH difference between 7.0 and 6.8 represent a change of two times more Hydrogen ions than hydroxide ions making the solution acid.

What does this mean in terms of fish health: in some ways not much and in other ways trouble is waiting just around the corner. Fortunately for fish keepers most freshwater fish can tolerate a very wide range of pH. We fish keepers are led falsely to grab on to the idea that freshwater fish can thrive only in water with optimum pH rating. Generally speaking most freshwater fish can be moved from one pH to another with the most important aspect of this movement in pH is fresh water fish should not be moved into a pH that is outside their range of pH, freshwater fish can and do thrive in a very wide pH range.


The key is accumulation the slow movement which is usually anywhere between 6.5 and 8.5 pH for freshwater fish (this movement in terms of gaining the greatest benefit should not exceed a change greater than .3 tens of an integer at a time). This ability allows the water critter to occupy a greater environmental niche expanding and contracting as pH changes throughout the day and night.


The character of water’s pH is not as important as stability of the character that is pH; as long as freshwater fish are within the necessary pH range that supports complete function of life giving physiological processes, the fish will thrive. For fish the usable range of pH can depend on several factors including prior pH acclimatization water temperature the amount of dissolved oxygen and the amount of cations and anions present in the water. History of gradual movement in pH is what is required.

pop 07-10-2014 04:12 PM

ramble continued
 
DARK POWER OF HYDROGEN
When you encounter the dark side of pH trouble quickly follows: a number of folks have suggested that in acidic conditions pH lower than 6.0 hydrogen ions can become toxic to fish due to the fish’s reaction of producing mucus on the gills epithelium which reduces the free exchange respiratory gasses and ionic exchange with the surrounding waters. In this state of respiration distress and osmotic imbalance become the basic symptom of acid stress in freshwater fish.

In situations where the surrounding waters are basic to the point of reaching or passing the limit of toleration Hydroxide ions will strip the slime coat from the fish and the high alkaline level will burn the skin of the fish and other exposed surface areas as gills and eyes. At this level of pH the ability to dispose metabolic waste ceases to function. These are extreme situations and are used only to show the how extensive pH can affect other substances.
Synergism is a vague concept and for us fish keeper’s synergism means substances as ammonia can become more toxic as the surrounding water moves towards more basic condition. This ability to enter a synergistic state represents the most significant environmental impact in our aquariums by ph.
This occurs when the water’s pH changes due to say the presents of carbon dioxide from respiration lowers the pH and combines with ammonia ions derived from fish waste chemically react and form harmless ammonium ions and hydroxyl ions and carbon dioxide. This synergistic state is one of great value to us fish keepers, sadly the tables can turn and as hydroxyl ions are created the pH rises perhaps due to photosynthesis and becomes more basic and changes the harmless ammonium back into toxic ammonia.
The changes in toxicity not only occur with the ammonia ion it also interacts with other substances in the water as total dissolved or total suspended substances. The toxic potential of other substances as iron consider 4 mg/l of iron at a pH of 4.8. would not present a synergistic state, yet a volume of .9 mg/l at a pH 5.5 of iron would enter a synergistic state resulting in unexpected appearance of a toxic substance endangering the healthy environment of your aquarium.
Salvation
Fortunately we fish keepers are saved from the tyranny of pH synergism by water hardness. Water hardness is the balance and brings strength of stability to water chemistry, resulting in the healthy and thriving environment of the aquarium. Water hardness strength of stability restricts pH’s willingness to enter or leave a synergistic state affecting the toxicity of many different substances. Water hardness also has a direct effect on the vital processes of osmoregulation that is essential for healthy fish.
Water hardness is the measurement of divalent mineral ions as calcium, magnesium, iron and zinc to list a few and are acquired as rain water absorbs surrounding’s substances. Water hardness comes in two flavors permanent hardness and alkalinity or carbon hardness and when the two types of hardness are combined they are referred to as general hardness.
Alkalinity is the form of hardness that comes from carbonate and bicarbonate ions that directly indicates the buffering capacity of the water that results in this hardness becoming a consumable providing strength of stability, that is replenished by frequent water changes is necessary.

The strength of stability in pH is derived from the carbon dioxide/bicarbonate/carbonate buffering system.
This system stabilizes pH by collecting extra hydrogen ions and then release these captured hydrogen ions as the pH rises, maintaining stability. When fish and plants release carbon dioxide from respiration some of the CO2 dissolves in water to form carbonic acid.
When the water becomes more alkaline, from perhaps plant photosynthesis, the carbonic acid dissociates to form bicarbonate and hydrogen ions. Since hydrogen ions are acid they counter the change caused by a increase of alkalinity. If the alkalinity continues to increase the bicarbonate dissociate to form solid carbonate and release more hydrogen ions developing continued pH stability.
If the pH should drop the stabilizing works in reverse collecting and capturing excess hydroxide ions and releasing these ions as needed providing the strength of stabilization. Water’s capacity to control pH’s wandering into a synergistic state is dependent on the amount of bicarbonate and carbonate available for duty.

Sources:
http://www.swrcb.ca.gov/rwqcb5/water_issues/basin_plans/ph_turbidity/ph_turbidity_04phreq.pdf
http://www.lenntech.com/aquatic/acids-alkalis.htm
http://www.state.ky.us/nrepc/water/wcpph.htm
http://www.ehow.com/info_12101588_can-ph-affect-fish.html
http://www.cichlid-forum.com/articles/hardness.php


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