Curious pH question. - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 6 Old 06-16-2011, 09:50 PM Thread Starter
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Curious pH question.

I am just wondering, what are the effects on a fish if the pH of the water it is living in is too low for its recommended range? Or two high for its natural environment?
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post #2 of 6 Old 06-17-2011, 01:23 AM
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[quote=Jadgpanther4tw;703139]I am just wondering, what are the effects on a fish if the pH of the water it is living in is too low for its recommended range? Or two high for its natural environment?[/quot

Most fishes will adapt to the pH so long as it is stable. It is only when we begin trying to change the pH with powders and potions that fishes begin to struggle.
Ideally, you want to keep fishes that will do well with the pH you have from the tap as this will provide the most stable enviornment.
It is the hardness (GH) that affects the fishes more than the pH. Keep fishes that like hard water in hard water, and keep softwater fishes in soft water.They will do poorly otherwise.

The most important medication in your fish medicine cabinet is.. Clean water.
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post #3 of 6 Old 06-17-2011, 02:44 AM Thread Starter
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I guess more of what i was getting at is a definition of "doing poorly" is. Like...symptoms of a fishing having trouble with ph or hardness issues. And if they can lead to death?
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post #4 of 6 Old 06-17-2011, 03:04 AM
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Not sure if this helps! Below article copied from.... d=1

What Is pH And How Does It Affect Your Fish?

pH defines how acidic or basic the water is. The term "pH" describes the amount of hydrogen (H+) and hydroxide (OH-) ions dissolved in a solution. (For those who are interested, in mathematical terms pH is defined at the negative log of the hydrogen ion concentration.) The more hydrogen ions there are, the more acidic the water is and the lower the pH is. A solution that has equal concentrations of hydroxide and hydrogen is termed neutral with a pH value of 7. A higher concentration of hydroxide ions would return a value above 7 or alkaline. A higher concentration of hydrogen ions would return a value below 7 or acidic. The pH scale is logarithmic, in other words, each step up or down is 10 times that of the previous one. A pH of 6 is ten times more acidic than a pH of 7. A pH of 5 is a 100 times more acidic than 7 and so on.

Most freshwater fish live within a pH range of 5.5 to 7.5 (African chiclids can go up to 8.4). Since the scale is logarithmic, this range represents a variation of over a 1000 times. Even an apparently small change in pH can affect fish, causing stress or death.

The consequences for fish are many and varied. It affects their breathing ability. High acidity or alkalinity can cause direct physical damage to skin, gills and eyes. Prolonged exposure to sub-lethal pH levels can cause stress, increase mucus production and encourage epithelial hyperplasia (thickening of the skin or gill epithelia) with sometimes-fatal consequences.

There are indirect consequences that can also affect fish. Changes in pH will affect the toxicity of many dissolved compounds. For example, ammonia becomes more toxic as pH increases. Fluctuations in pH, even though they may still be within the preferred range, can be stressful and damaging to fish health. Nitrifying bacteria, essential in the conversion of ammonia to nitrate also have a pH range preference, which is between 7.5 and 8.6. Variations in pH will also have an effect on some disease treatments. Chloramine-T is more toxic at low pH, while potassium permanganate is more dangerous at high pH.

Monitoring the pH in an established aquarium can often indicate water change and substrate vacuuming needs, or a clogged under-gravel filter. Excess waste product produces carbonic acid, which acidifies the water and lowers the pH.

While selecting fish that are compatible to the pH of the water used to fill the aquarium is the best method and avoids the need to change the pH, many aquarists want keep a species of fish that may require pH alteration. Many fish can accept a limited pH range, however breeding may be more difficult if not impossible. There are methods of altering the pH in your aquarium.
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post #5 of 6 Old 06-17-2011, 11:01 AM Thread Starter
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very helpful infact. It was informative and more along the lines of what i was wondering about. I wonder if this person who put that article together knew about substrate that buffers a certain ph lvl? Like crushed coral will naturally buffer any water to 8.2.
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post #6 of 6 Old 06-17-2011, 03:10 PM
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The passage cited in post #4 is correct, but one sentence in that could be misunderstood, so allow me to explain. The sentence is,

Most freshwater fish live within a pH range of 5.5 to 7.5 (African cichlids can go up to 8.4).

This does not mean that all fish can manage within the range given, far from it. What it does mean is that all aquarium fish fall somewhere within this range.

Many commonly-available fish are tank-raised and adapt more or less to a slightly wider range than they would have in the wild. But there are still some specifics. Livebearers require medium hard to hard water (which has a corresponding higher pH, anywhere from 7 to 9 depending upon the hardness and which minerals cause it), rift lake cichlids the same and better at the higher end of hardness and pH. Soft water fish do best in soft to medium hard water with a correspondingly lower pH, somewhere between 6 to 7.6 depending upon species. Wild caught soft water fish will not do well unless the water is soft with a lower pH though this can vary a bit since it is the hardness that is actually critical.

Many soft water fish do not last as long as their respective lifespan when kept in hard water. Calcium blocks the kidneys for one thing, and there are other similar issues. This is not detectable externally, the fish may "appear" fine, but suddenly it dies after say 3-4 years instead of the normal 10 years. This particular example is the cardinal tetra. The species will externally look the same in soft water or hard water, but internally trouble is there and the fish up and dies sooner than it should.

Selecting the substrate is important for the buffering aspect you mention. Substrates for a tank of soft to medium hard water fish should not contain calcareous substances (limestone, dolomite, marble, tufa, coral) as these will raise the hardness further, and corresponding the pH. This type of substrate is ideal for rift lake cichlids, and livebearers, along with those other species that are best in such an environment naturally. An inert substrate material will not affect water chemistry of itself, though what naturally occurs in the substrate will. But that is another topic.

The pH is important because fish must adjust their internal (blood) pH to match their surrounding water. This is one reason why pH fluctuations are so dangerous, if they are significant. A minor fluctuation of less than 1 d pH over a period of time is tolerable, and in fact natural. Planted tanks for example have a diurnal pH fluctuation of several decimal points, say from 6.0 to 6.5 during the day and then back again during darkness. There is no issue for fish in this, because it is what often occurs in their habitat waters and it is spread out over 24 hours and occurs slowly. So back to the internal pH, a fish programmed by nature to live in water with a pH of 4-5 is going to have to adjust its blood pH a lot to manage in a pH of 8. And many cannot do this. But as I mentioned earlier, the corresponding hardness is also of equal significance.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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