Are Koi wusses? Part V - pH

The pH of water is important, not only to Fish, but to all aquatic life because pH affects the ability of fish and other aquatic organisms to regulate basic life-sustaining processes, primarily the exchanges of respiratory gasses and salts with the water in which they live. Inability to adequately regulate these processes can result in numerous non-lethal effects  and even mortality, in cases when  pH exceeds the normal range physiologically tolerated by aquatic organisms.

Unfortunately, there is no definitive pH range that is safe for all aquatic organisms. The acceptable pH range for aquatic life, especially fish, is dependent on other factors, including, but not limited to, prior pH acclimatization, water temperature, and dissolved Oxygen levels.

Our focus is the adaptability of Carp (Koi). Let’s look at some limits that have been determined by various studies.

-The lower pH limit for Carp (Koi) is between 5.0 and 5.5. Below this mortality occurs.

-The growth rate of Carp (Koi) is reduced at pH levels of 5.5 to 6.0.

-At pH levels of 8.0 to 8.5, the motility of Carp (Koi) sperm is reduced, thusly affecting the spawning process.

-Carp (Koi0 avoid pH levels of 9.0 to 9.5 (Goldfish avoid levels of 8.5 to 9.0). 

-Carp (Koi) cannot survive at pH levels over 11.0.

-Carp (Koi) lose the ability to absorb Oxygen as pH decreases, with this becoming increasingly more severe at pH levels below 6.5.

We can see, as a result, that Carp (Koi) can survive in a pH range of 5.5 to 11.0. This may be the survival range, but is definitely not what we have termed a ‘Comfort Zone”.

The consensus of all examined sources would indicate that this pH ‘Comfort Zone’ is 6.5 to 8.5. This is further substantiated by the results of a test that showed that Carp (Koi) could be moved between different pH levels without any chronic effects as long as both pH levels fell within this range of 6.5 to 8.5. Any effects that were caused were temporary and non-lethal with the fish adapting and returning to normal within a short time. However, if the fish were transferred to a pH outside of this range from any level within this range, chronic effects or mortality usually occurred. In other words, Carp (Koi) will adapt to a sudden pH change of 6.5 to 8.0, but will suffer permanent physiological damage and even death if suddenly transferred from 8.5 to 9.0. They can adapt to changes outside of the ‘Comfort Zone’ when these changes are gradual  This is evident in the fact that they are subject to diurnal fluctuations in pH in their natural environs, with the lowest being at dawn and the highest being in late afternoon, either or both of these levels being outside of their pH ‘Comfort Zone’.

Not only is this pH range of 6.5 – 8.5 ideal for Carp (Koi), except during spawning where a range of 6.5 - 8.0 is more suitable. It has also been proven that  the range of 6.5 - 8.5 will promote the most diverse, healthy and productive aquatic life.

In our next post, we will begin discussing the Nitrogen cycle starting with Ammonia.

Are Koi Wusses? Part IV-Oxygen

Oxygen comprises 21% of the Earth’s atmosphere by volume and is vital to the existence of all higher animals. Some animals have developed, over time, an amazing efficiency in the utilization of Oxygen. Fish make up a large part of this group, with some being even more efficient than others. Members of the Carp family are some of these fish.

Fish respiration is very efficient. They possess the ability to remove up to 80% of Oxygen in water. Compare this to an efficiency rate of 27% for humans and it is quite impressive, but it is also necessary given the fact that, in fresh water, the normal level of oxygen, by volume, is 6-8 mg/L which is a tiny fraction of 1%.

Added to this amazing ability is the fact that members of the Carp family have the means to survive, for a period of time, at very low (hypoxic) oxygen levels. Goldfish (Carassius auratus auratus) can actually survive for extended periods with NO Oxygen (Apoxia).

Oxygen in the aquatic environment is usually measured in mg/L and in percent of saturation. Saturation is the normal maximum level of Oxygen that water can hold at a given temperature and atmospheric pressure. Water with no oxygen is termed  anoxic, 1% to 30% saturation is termed hypoxic, 31% to 100% is termed normoxic and any level over 100% is termed hyperoxic.

A “healthy” aquatic system should rarely experience less than 80% saturation. This means, for example, that a Pond that is located at sea level with a water temperature of 20C/68F should have an oxygen level of at least 7.3 mg/L. This same Pond at 26C/79F should have a minimum level of 6.6 mg/L. This lower level is because water loses its ability to retain Oxygen as temperatures increase, so saturation levels decrease.

One study states that Carp (Koi) can survive for 5hrs at 15C/59F under anoxic conditions. This adaptability is in inverse relation to temperature. As temperature rises, the time period of toleration decreases.

What about hyperoxia or super-saturation? Experiments have shown that “hyperoxia did not cause any visible changes in fish behavior, but at the biochemical level a serious stress was indicated. In fact, tissue-specific changes……did not return to normal even after 36 hrs of normoxic recovery”(Lushchak et. al. 2005).

So what does all of this mean?

As stated previously, Carp (Koi) are extremely adaptive. They can tolerate extremes in Oxygen levels for limited periods of time with no adverse effects given sufficient recovery time. Oxygen levels between 31% and 100% saturation are acceptable. The lower limits of this range are, however, not recommended. This is due to the fact that in any 24 hour period Pond Oxygen levels will fluctuate as temperatures change. A 40% saturation at noon will most probably mean an anoxic condition existed pre-dawn. 70% saturation is suitable for Carp (Koi), but 80% saturation is best for the entire eco-system.

How important is pH? Next!

Are Koi Wusses? Part III-Temperature

 “It’s hot enough to fry an egg!”  “It’s colder than a well-digger’s….”

Descriptive phrases meant to indicate that the prevailing temperatures are outside of our human ‘comfort zone’. Do Carp (Koi) have comfort zones as relates to temperatures? In a manner of speaking, the answer is… Yes! Temperature has a direct effect on the physiological processes of Carp (Koi).

Every living organism has a temperature range in which they easily maintain what is termed homeostasis. Homeostasis is defined as:  the tendency of a system, esp. the physiological system of higher animals, to maintain internal stability, owing to the coordinated response of its parts to any situation or stimulus tending to disturb its normal condition or function. (Dictionary.com)

Outside of this range, discomfort (stress) occurs as an organism attempts to adapt. If the variance is far enough outside the ‘comfort zone’, the organism is unable to adapt, stress becomes too great and mortality occurs.

When we are cold, we shiver. When we are hot, we perspire. We exhibit noticeable signs. A Carp (Koi), however, does not shiver or sweat. So how are we able to determine the ‘comfort zone’ of Carp (Koi), as relates to temperature?

 Respiration!!

The results of a study by the Agricultural Institute, University of Louvain (Belgium) published in 1957 show that Carp (Koi) exhibit a fairly stable respiratory rate between 20C/68F and 34C/93F. Above this range, the respiration rate rapidly increases until death occurs at 36C/97F for large fish and  38C/100F for small fish. Below this range, the respiration rate decreases and becomes extremely slow, One (1) every 60 seconds at 4C/39F. This study did not encompass temperatures below 4C/39F.

Even though no discomfort (stress) is manifested between 20C/68F and 34C/93F, ideally we want the temperature to be close to the midpoint of this range which is 27.5C/81-82F.  This is well above the median temperature recommended by many sources, but is shown to be the ideal temperature for the Carp’s (Koi’s) optimum metabolism.

Temperature is as influential on the health and well-being of Carp (Koi) as are the other factors mentioned in the previous post.

Carp are extremely adaptable fish, but even this adaptability has it’s limits, the main one being time. Any acclimation to a new environment, or even one environmental factor or parameter, must be gradual. This includes temperature. The adaption period in abrupt temperature changes may run from 48 hours to as much as 14 days in extreme cases and even mortality if the temperature differential is too great. During this period the fish will be stressed  One way that this stress will manifest is Ammonia autointoxication, which we will cover in a later post. The old admonition, when adding new fish to a Pond,  to always float the bag containing the fish for 15-20 minutes does not really accomplish anything. The fish will continue to adapt to the temperature change for probably several days. 

Next: Oxygen

Are Koi wusses? Pt. II-General Parameters

Koi (Cyprinus carpio) are probably one of the world's most adaptable specie of fish. Originating in the Caspian, Black and Aral Seas where they mostly inhabited the river deltas, such as the Danube, they developed the physiology to thrive in eutrophic (characterized by an abundant accumulation of nutrients that support a dense growth of algae and other organisms, the decay of which depletes the shallow waters of oxygen in summer) waters. These are waters that are heavy in phosphates and nitrates which promote abundant plant growth and which also support a very diverse and complex Food Web. These conditions are, in part,  duplicated in the mud ponds used by Koi breeders.

These conditions, however, are not desirable in a Water Feature that is part of one's personal landscape.The fantastic, and sometimes dazzling, coloration of Koi can only be fully appreciated in waters that are clear. Water clarity, or lack of, does not appear to have any physiological effect on Carp There are, however, other chemical water quality parameters that DO

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Any Pondkeeper knows, or certainly should know, that chemical factors such as pH, Ammonia, Nitrite, Nitrate, Dissolved Oxygen along with Alkalinity, Hardness, Phosphate, Salinity and Temperature can affect the health and longevity of every aquatic organism, including fish. But what are the desired quantitative levels of these various factors? Well......It seems that there is a wide range of recommendations as evident in the chart below. This chart shows suggested levels from retailers, breeders, organizations and governmental agencies.

Parameter	Source a	Source B	Source C	Source D	Source E
pH	6.5 – 9.0	7.2 – 7.8	7.5 – 8.5	6.0 – 8.0	7.0 – 8.0
Ammonia	<.1 ppm	N/A	0	0 - .08 mg/l	0 - .01 mg/l unionized
Nitrite	< .2 ppm	0.0-.3 ppm	0 – .4 ppm	0 - .06 mg/l	0 - .01 mg/l
Nitrate	< 50 ppm	< 80 ppm	0 – 200 ppm	N/A	9 – 20 mg/l
Dissolved Oxygen	> 5.0 mg/l	N/A	9 mg/l @ 50F	4 – 10 mg/l	8 – 12 mg/l
Temperature	N/A	N/A	79F – 81F	65F – 75F	65F – 77F
Alkalinity	50 -170 ppm	N/A	120 – 180 ppm	50 – 350 mg/l	100 – 250 mg/l

As can be seen, the range of recommendations is quite varied and large

This chart, at first glance, is confusing. Who's recommendation is correct?

Well, in actuality, as relates to Carp, they all are! This attests to the adaptability of Carp.

In successive posts, we will take a closer look at each of these chemical factors.  Next up: Temperature.

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