Substrate questions

It depends on the definition of thriving, I guess. If they live for years, are eating well, interacting, and colored well, I would call that thriving. Fish tend to show us when something is wrong.

Edit: I don't mean this to sound snarky, Byron. I'm just wondering, what is it that tells you your fish are thriving now, and weren't before? Is there some difference in their appearance or behavior?
 
It depends on the definition of thriving, I guess. If they live for years, are eating well, interacting, and colored well, I would call that thriving. Fish tend to show us when something is wrong.

Edit: I don't mean this to sound snarky, Byron. I'm just wondering, what is it that tells you your fish are thriving now, and weren't before? Is there some difference in their appearance or behavior?

I don't mind the discussion, and you are quite right to ask the question.

We can only expect that our fish are likely thriving when we provide what they need/expect, and that comes from research into the habitat conditions and fish physiology. I have discussed this with Neale Monks and Ian Fuller, and you can read the same in The Manual of Fish Health which was written by three of the most respected individuals in the hobby. Fish have a very strong sense of survival, as do most animals, and they will swim, eat and spawn if they possibly can in spite of negatives; this should not be assumed to be "thriving."

When I had my cories over gravel for many years, before I knew better, they looked OK to me. But they could not filter feed as they "expect" to do, and that was most likely not the best situation. We cannot talk to our fish to find out, and to be honest I don't believe anyone can ascertain this just because the fish may be acting "normal" to our thinking. If they are being denied something they expect (because it is programmed into their DNA), we can only assume from our knowledge of biology that things could be better. We can never replace nature when we put fish in an enclosed space of an aquarium, but we can ensure they are being given all that we can provide from our study of their habitat and knowing how they interact with it. No land animal has the complicated interaction with its environment comparable to that of fish.
 
What grade grit do you use?
Is it the silicon carbide grit?
Does it cause more algae issues?
 
I think I may have to go feel some different sands to see the difference.
I was really hoping to find something in black that didn’t cost a fortune.
 
I don't mind the discussion, and you are quite right to ask the question.

We can only expect that our fish are likely thriving when we provide what they need/expect, and that comes from research into the habitat conditions and fish physiology. I have discussed this with Neale Monks and Ian Fuller, and you can read the same in The Manual of Fish Health which was written by three of the most respected individuals in the hobby. Fish have a very strong sense of survival, as do most animals, and they will swim, eat and spawn if they possibly can in spite of negatives; this should not be assumed to be "thriving."

When I had my cories over gravel for many years, before I knew better, they looked OK to me. But they could not filter feed as they "expect" to do, and that was most likely not the best situation. We cannot talk to our fish to find out, and to be honest I don't believe anyone can ascertain this just because the fish may be acting "normal" to our thinking. If they are being denied something they expect (because it is programmed into their DNA), we can only assume from our knowledge of biology that things could be better. We can never replace nature when we put fish in an enclosed space of an aquarium, but we can ensure they are being given all that we can provide from our study of their habitat and knowing how they interact with it. No land animal has the complicated interaction with its environment comparable to that of fish.
Can you please put up the links about Cory's being filter feeders and that that behavior is programmed into their DNA. I haven't been able to find this information anywhere.
 
Can you please put up the links about Cory's being filter feeders and that that behavior is programmed into their DNA. I haven't been able to find this information anywhere.

It is a matter of biology. All species on this planet evolved over time, and what makes each species unique is their DNA. There is no one to "teach" newly-hatched fish how to survive; they know because it is part of their DNA, and this includes how they find their food. As for how the corydoradinae feed, all one has to do is observe these fish in any/all of their habitats.
 
I still feel that corydoras are not highly enough evolved to be able to determine the difference between a crustacean and a piece of sand, therefore like I have stated before, I feel that sand annoys these guys rather than makes them happy.
 
I still feel that corydoras are not highly enough evolved to be able to determine the difference between a crustacean and a piece of sand, therefore like I have stated before, I feel that sand annoys these guys rather than makes them happy.

If you are not willing to learn, there is little point in asking the questions. You are free to reject proven fact, leave it at that.
 
I am wanting to learn that is why I have asked for the link showing the universty study on corydoras DNA. I am fascinated by this type of study.
 
Fish have a very strong sense of survival, as do most animals, and they will swim, eat and spawn if they possibly can in spite of negatives; this should not be assumed to be "thriving."
Agreed. All of us living things do what needs to be done to live and pass on the genes. But on the other hand, most experienced fish keepers know what sick, unhappy fish look like. If their colors are vibrant, if they are eating and digesting well, if they are acting alert and lively, and showing what appear to be normal social interactions, I think it's reasonable to assume they are thriving.
We cannot talk to our fish to find out, and to be honest I don't believe anyone can ascertain this just because the fish may be acting "normal" to our thinking.
I think that's the problem. Our fish don't talk to us. All we have to go on is what we can observe.

Wanting to recreate a fish's native environment, and give it all the things it expects, is a very admirable goal. But unless all of our tanks are strict biotopes, our fish are going to end up coping with situations that don't exist in their normal environments. Actually, even then we aren't going to give them what they expect, because fish in the wild don't normally have to cope with confinement unless they live in seasonal streams. (I believe, by the way, this is part of the reason panda garra, even wild-caught ones, are so tough and adaptable and take to captivity so easily) I don't think that means they can't thrive. Going beyond the basic research, the only way I have of knowing what the fish "expect," or which details of their habitat are critical to their well-being, is by observing their appearance and behavior.

I've had cories behave and appear like healthy fish over multiple years, on "rough" sand, giving no signs of distress or discomfort from same. I know several others who have similar experiences. Lacking overwhelming evidence to the contrary, I have to go with what my eyes see and conclude that it isn't harmful to them.
 
If everyone kept their Cory's on Amazonian sand I would have no problem with that. But aquarist's are keeping Cory's on all sorts of sands, and that is my concern. Play sand, filter sand, volcanic sand. My concern is that some of these are going to consist of sharp pieces of silica that is going to damage the fishes gills and gut and we are not considering that on the long term well being of the fish. If you want to keep Cory's on sand then make sure it is Cory safe. Amazonian sand that they would have had in the wild. Not on any man made sand bought from a DIY store.
 
I am wanting to learn that is why I have asked for the link showing the universty study on corydoras DNA. I am fascinated by this type of study.

I don't know why you can't fathom it, but this DNA issue is simply the fact of how all life on this planet "lives." The DNA of each living organism is the genetic instructions for that particular species. It has all the instructions that a living organism needs to grow, reproduce and function. DNA thus determines the size, colour, behaviours, feeding habits, etc of the species.
 
Agreed. All of us living things do what needs to be done to live and pass on the genes. But on the other hand, most experienced fish keepers know what sick, unhappy fish look like. If their colors are vibrant, if they are eating and digesting well, if they are acting alert and lively, and showing what appear to be normal social interactions, I think it's reasonable to assume they are thriving.

I think that's the problem. Our fish don't talk to us. All we have to go on is what we can observe.

Wanting to recreate a fish's native environment, and give it all the things it expects, is a very admirable goal. But unless all of our tanks are strict biotopes, our fish are going to end up coping with situations that don't exist in their normal environments. Actually, even then we aren't going to give them what they expect, because fish in the wild don't normally have to cope with confinement unless they live in seasonal streams. (I believe, by the way, this is part of the reason panda garra, even wild-caught ones, are so tough and adaptable and take to captivity so easily) I don't think that means they can't thrive. Going beyond the basic research, the only way I have of knowing what the fish "expect," or which details of their habitat are critical to their well-being, is by observing their appearance and behavior.

I've had cories behave and appear like healthy fish over multiple years, on "rough" sand, giving no signs of distress or discomfort from same. I know several others who have similar experiences. Lacking overwhelming evidence to the contrary, I have to go with what my eyes see and conclude that it isn't harmful to them.

I researched the issue of stress for an article some time ago, and it may be instructive to post it here. I think the evidence shows that we can never assume the fish are "thriving" or even healthy from outward observation because of the complex life processes. The article is lengthy, but here it is.

Stress and Freshwater Aquarium Fish
Stress is the root cause of almost all disease and health problems of aquarium fish. Today we recognize that the health of any living organism is directly related to the level of stress inflicted upon it; for fish this is a major problem because the fish cannot do anything to reduce or eliminate it—they can only fight it or succumb to it. Our fish are confined to the small space of their aquarium, and only the aquarist can control their environment. In a very real sense, we are directly responsible for any and all stress inflicted upon the fish. Later we’ll consider how this occurs, but before that we must understand what stress is and how it harms our fish. Here is how Biology Online defines stress:​
The sum of the biological reactions to any adverse stimulus—physical, mental or emotional, internal or external—that tends to disturb the organisms homeostasis; should these compensating reactions be inadequate or inappropriate, they may lead to disorders.​
Homeostasis is defined as “the tendency of an organism or a cell to regulate its internal conditions, usually by a system of feedback controls, so as to stabilize health and functioning, regardless of the outside changing conditions.” Physiological homeostasis, or physical equilibrium, is the internal process animals use to maintain their health and life: “the complex chain of internal chemical reactions that keep the pH of its blood steady, its tissues fed, and the immune system functioning” (Muha, 2006).​
Four important body functions of homeostasis are closely associated with processes in the gills: gas exchange, hydromineral (osmoregulation) control, acid-base balance [pH] and nitrogenous waste excretion [ammonia]. These processes are possible because of the close proximity of the blood flowing through the gills to the surrounding water, as well as the differences in the chemical composition of these two fluids (Bartelme, 2004). Each species of fish has evolved within a specific environment—and by “environment” in this context we mean everything associated with the water in which the fish lives—and the physiological homeostasis only functions well within that environment. This greater dependence upon their surrounding environment is why fish are more susceptible to stress than many other animals (Wedemeyer, 1996).​
How Stress Affects Fish
Stress is caused by placing a fish in a situation which is beyond its normal level of tolerance (Francis-Floyd, 1990). Stress makes it more difficult for the fish to regulate the normal day-to-day physiological functions—the homeostasis—that are essential to its life. Dr. Cliff Swanson, associate professor at North Carolina’s College of Veterinary Medicine, says that stress creates “a fundamental physiological shift in fish, from energy storage to energy usage—the fight or flight response” (Muha, 2005). The survival of any organism depends upon its ability to keep its internal chemical balance from fluctuating too much. When critical energy is being used to fight stress, it is diverted away from other functions. The fish must then work much harder just to “keep going.” Laura Muha (Muha, 2006) likens this to driving a car up a steep hill: it takes more gas (energy) and effort to maintain the same speed as on level ground (level being the norm for the fish).​
The effects of stress on fish are very complicated physiologically, and are often subtle. There may or may not be external signs discernible to us—it can continue for weeks and even months, sometimes up to the point when the fish just suddenly dies. The reasons for this are involved.​
Adrenaline released during the stress response increases blood flow to the gills to provide for the increased oxygen demands of stress. The release of adrenaline into the blood stream elevates the heart rate, blood flow and blood pressure. This increases the volume of blood in vessels contained within the gills, increasing the surface area of the gills to help the fish absorb more oxygen from the water. The elevated blood flow allows increased oxygen uptake for respiration but also increases the permeability of the gills to water and ions. This is what is known as the osmorespiratory compromise (Folmar & Dickhoff, 1980; Mazeaud et al., 1977). In freshwater fish, this increases water influx and ion losses. This is more critical in small fish than larger due to the gill surface to body mass ratio (Bartelme, 2004).​
Short-term stress will cause an increase in heart rate, blood pressure, and respiration as described in the preceding paragraph. The fish can only maintain these altered states for a short and finite period of time before they will either adapt or (more often) the stress will become chronic. During this initial stage the fish may look and act relatively normal, but it is depleting energy reserves because of the extra physiological requirements placed upon it. At the chronic stage the hormone cortisol is released, which is responsible for many of the negative health effects associated with stress.​
One of the most characteristic aspects of stress in fish is osmoregulatory disturbance, which is related to the effects of both catecholamine and cortisol hormones. The extent of the disturbance following stress depends upon the ionic and osmotic gradients (difference) between the internal fluids of the fish and its surrounding environment (water)—something we will explore in more detail later. If the stress is persistent and of sufficient intensity, changes in the cellular structure of the gills may occur under the influence of cortisol. In this situation, increased death and turnover rates of branchial epithelial cells leads to accelerated aging of the gills. These degenerating and newly-formed gill cells do not function normally, which further limits the fish's ability to maintain water and ion homeostasis under stressful conditions. Thus, acute stress limits the fish's capacity to osmoregulate, and prolonged periods of extreme stress may result in osmotic shock and death (Bartelme, 2004).​
Chronic stress impacts negatively on fish growth, digestion, and reproduction. It is the main cause of deterioration in the slime coat. It significantly lowers the ability of the immune system to respond effectively and fully. And in all cases—stress reduces the fish’s lifespan.​
The slime coat or mucus layer is a physical barrier that inhibits entry of disease organisms from the environment into the fish. But it is also a chemical barrier because it contains enzymes (lysozymes) and antibodies (immunoglobulin) which can kill invading organisms. Mucus also lubricates the fish which aids movement through the water, and it is also important for osmoregulation (Francis-Floyd, 1990).​
This deteriorated slime coat, along with a lowered immune response, is what allows parasites, bacteria, pathogens, protozoans and fungi to infect the fish and cause disease. More water enters the cells, further impacting osmoregulation and increasing work for the kidneys. The effects of stress on the immune function can linger for some time after other physiological changes have returned to pre-stress levels (Maule et al., 1989).​
There are really only two requirements for a disease to occur in a fish: first, the pathogen must be present; and second, the fish must be under sufficient stress to weaken the immune system to enable that pathogen to actually cause an infection. The very few pathogens that can cause an infection without any stress in the fish are quite rare. Clearly, the best disease prevention is to eliminate stress as much as possible​

The Causes of Stress

[There is more to this section, but for brevity I will just include the summation.]​

Each species of fish has evolved over thousands of years to live in a particular environment. The water chemistry along with the environmental factors of the habitat are crucial not only to the life of the fish but to the state of its health during that life. As we learned above, the fish’s homeostasis only functions well within the species’ natural environment. A normal lifespan is virtually impossible if the fish’s environmental needs are not met to some extent. For instance, if one intends to house tropical forest fish, “the chemical and physical properties of aquatic environments associated with rainforests must be duplicated, or at least approximated, in order to keep these fishes in the best of health” (Weitzman et al., 1996).​

References:

Bartelme, Terry D. (2004), “Short Take: Stress In Fish, Part II: Why You Should Care About Stress In Fish,” Advanced Aquarist online: http://www.advancedaquarist.com/2004/9/fish2

Drs. Foster & Smith LiveAquaria, Stress and Fish Health: http://www.liveaquaria.com/PIC/article.cfm?aid=88

Evans, Mark E. (2004), “The Ins & Outs of Osmosis,” Tropical Fish Hobbyist, February 2004.

Francis-Floyd, Ruth (1990), “Stress—Its Role in Fish Disease,” CIR919 (December 1990), Fisheries and Aquatic Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.

Maule, A.G., R.A. Tripp, S.L. Kaattari, & C.B. Shreck (1989), "Stress Alters Immune Function and Disease Resistance in Chinook Salmon (Oncorrhynchus tshawytscha)," Journal of Endocrinology, 120, 135-142, 1989.

Muha, Laura (2005), “Stress” in “The Skeptical Fishkeeper” column, Tropical Fish Hobbyist, December 2005.

Muha, Laura (2006), “Fish Growth vs. Tank Size” in “The Skeptical Fishkeeper” column, Tropical Fish Hobbyist, December 2006.

Narten, Thomas, “Fish Stress and Healthy Fishkeeping,” The Aquaria FAQ at http://fins.actwin.com/mirror/

Wedemeyer, G.A. (1996), "Transportation and Handling," in Principles of Salmonid Culture, W. Pennell and B.A. Barton (eds.), pp. 727-758. Cited in Bartelme (2004).

Weitzman, Stanley H., Lisa Palmer, Naercio A. Menezes & John R. Burns (1996), “Maintaining Tropical and Subtropical Forest-Adapted Fishes,” Tropical Fish Hobbyist, June 1996.
 
Last edited:
I researched the issue of stress for an article some time ago, and it may be instructive to post it here. I think the evidence shows that we can never assume the fish are "thriving" or even healthy from outward observation because of the complex life processes. The article is lengthy, but here it is.

Stress and Freshwater Aquarium Fish
Stress is the root cause of almost all disease and health problems of aquarium fish. Today we recognize that the health of any living organism is directly related to the level of stress inflicted upon it; for fish this is a major problem because the fish cannot do anything to reduce or eliminate it—they can only fight it or succumb to it. Our fish are confined to the small space of their aquarium, and only the aquarist can control their environment. In a very real sense, we are directly responsible for any and all stress inflicted upon the fish. Later we’ll consider how this occurs, but before that we must understand what stress is and how it harms our fish. Here is how Biology Online defines stress:​
The sum of the biological reactions to any adverse stimulus—physical, mental or emotional, internal or external—that tends to disturb the organisms homeostasis; should these compensating reactions be inadequate or inappropriate, they may lead to disorders.​
Homeostasis is defined as “the tendency of an organism or a cell to regulate its internal conditions, usually by a system of feedback controls, so as to stabilize health and functioning, regardless of the outside changing conditions.” Physiological homeostasis, or physical equilibrium, is the internal process animals use to maintain their health and life: “the complex chain of internal chemical reactions that keep the pH of its blood steady, its tissues fed, and the immune system functioning” (Muha, 2006).​
Four important body functions of homeostasis are closely associated with processes in the gills: gas exchange, hydromineral (osmoregulation) control, acid-base balance [pH] and nitrogenous waste excretion [ammonia]. These processes are possible because of the close proximity of the blood flowing through the gills to the surrounding water, as well as the differences in the chemical composition of these two fluids (Bartelme, 2004). Each species of fish has evolved within a specific environment—and by “environment” in this context we mean everything associated with the water in which the fish lives—and the physiological homeostasis only functions well within that environment. This greater dependence upon their surrounding environment is why fish are more susceptible to stress than many other animals (Wedemeyer, 1996).​
How Stress Affects Fish
Stress is caused by placing a fish in a situation which is beyond its normal level of tolerance (Francis-Floyd, 1990). Stress makes it more difficult for the fish to regulate the normal day-to-day physiological functions—the homeostasis—that are essential to its life. Dr. Cliff Swanson, associate professor at North Carolina’s College of Veterinary Medicine, says that stress creates “a fundamental physiological shift in fish, from energy storage to energy usage—the fight or flight response” (Muha, 2005). The survival of any organism depends upon its ability to keep its internal chemical balance from fluctuating too much. When critical energy is being used to fight stress, it is diverted away from other functions. The fish must then work much harder just to “keep going.” Laura Muha (Muha, 2006) likens this to driving a car up a steep hill: it takes more gas (energy) and effort to maintain the same speed as on level ground (level being the norm for the fish).​
The effects of stress on fish are very complicated physiologically, and are often subtle. There may or may not be external signs discernible to us—it can continue for weeks and even months, sometimes up to the point when the fish just suddenly dies. The reasons for this are involved.​
Adrenaline released during the stress response increases blood flow to the gills to provide for the increased oxygen demands of stress. The release of adrenaline into the blood stream elevates the heart rate, blood flow and blood pressure. This increases the volume of blood in vessels contained within the gills, increasing the surface area of the gills to help the fish absorb more oxygen from the water. The elevated blood flow allows increased oxygen uptake for respiration but also increases the permeability of the gills to water and ions. This is what is known as the osmorespiratory compromise (Folmar & Dickhoff, 1980; Mazeaud et al., 1977). In freshwater fish, this increases water influx and ion losses. This is more critical in small fish than larger due to the gill surface to body mass ratio (Bartelme, 2004).​
Short-term stress will cause an increase in heart rate, blood pressure, and respiration as described in the preceding paragraph. The fish can only maintain these altered states for a short and finite period of time before they will either adapt or (more often) the stress will become chronic. During this initial stage the fish may look and act relatively normal, but it is depleting energy reserves because of the extra physiological requirements placed upon it. At the chronic stage the hormone cortisol is released, which is responsible for many of the negative health effects associated with stress.​
One of the most characteristic aspects of stress in fish is osmoregulatory disturbance, which is related to the effects of both catecholamine and cortisol hormones. The extent of the disturbance following stress depends upon the ionic and osmotic gradients (difference) between the internal fluids of the fish and its surrounding environment (water)—something we will explore in more detail later. If the stress is persistent and of sufficient intensity, changes in the cellular structure of the gills may occur under the influence of cortisol. In this situation, increased death and turnover rates of branchial epithelial cells leads to accelerated aging of the gills. These degenerating and newly-formed gill cells do not function normally, which further limits the fish's ability to maintain water and ion homeostasis under stressful conditions. Thus, acute stress limits the fish's capacity to osmoregulate, and prolonged periods of extreme stress may result in osmotic shock and death (Bartelme, 2004).​
Chronic stress impacts negatively on fish growth, digestion, and reproduction. It is the main cause of deterioration in the slime coat. It significantly lowers the ability of the immune system to respond effectively and fully. And in all cases—stress reduces the fish’s lifespan.​
The slime coat or mucus layer is a physical barrier that inhibits entry of disease organisms from the environment into the fish. But it is also a chemical barrier because it contains enzymes (lysozymes) and antibodies (immunoglobulin) which can kill invading organisms. Mucus also lubricates the fish which aids movement through the water, and it is also important for osmoregulation (Francis-Floyd, 1990).​
This deteriorated slime coat, along with a lowered immune response, is what allows parasites, bacteria, pathogens, protozoans and fungi to infect the fish and cause disease. More water enters the cells, further impacting osmoregulation and increasing work for the kidneys. The effects of stress on the immune function can linger for some time after other physiological changes have returned to pre-stress levels (Maule et al., 1989).​
There are really only two requirements for a disease to occur in a fish: first, the pathogen must be present; and second, the fish must be under sufficient stress to weaken the immune system to enable that pathogen to actually cause an infection. The very few pathogens that can cause an infection without any stress in the fish are quite rare. Clearly, the best disease prevention is to eliminate stress as much as possible​

The Causes of Stress

[There is more to this section, but for brevity I will just include the summation.]​

Each species of fish has evolved over thousands of years to live in a particular environment. The water chemistry along with the environmental factors of the habitat are crucial not only to the life of the fish but to the state of its health during that life. As we learned above, the fish’s homeostasis only functions well within the species’ natural environment. A normal lifespan is virtually impossible if the fish’s environmental needs are not met to some extent. For instance, if one intends to house tropical forest fish, “the chemical and physical properties of aquatic environments associated with rainforests must be duplicated, or at least approximated, in order to keep these fishes in the best of health” (Weitzman et al., 1996).​

References:

Bartelme, Terry D. (2004), “Short Take: Stress In Fish, Part II: Why You Should Care About Stress In Fish,” Advanced Aquarist online: http://www.advancedaquarist.com/2004/9/fish2

Drs. Foster & Smith LiveAquaria, Stress and Fish Health: http://www.liveaquaria.com/PIC/article.cfm?aid=88

Evans, Mark E. (2004), “The Ins & Outs of Osmosis,” Tropical Fish Hobbyist, February 2004.

Francis-Floyd, Ruth (1990), “Stress—Its Role in Fish Disease,” CIR919 (December 1990), Fisheries and Aquatic Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.

Maule, A.G., R.A. Tripp, S.L. Kaattari, & C.B. Shreck (1989), "Stress Alters Immune Function and Disease Resistance in Chinook Salmon (Oncorrhynchus tshawytscha)," Journal of Endocrinology, 120, 135-142, 1989.

Muha, Laura (2005), “Stress” in “The Skeptical Fishkeeper” column, Tropical Fish Hobbyist, December 2005.

Muha, Laura (2006), “Fish Growth vs. Tank Size” in “The Skeptical Fishkeeper” column, Tropical Fish Hobbyist, December 2006.

Narten, Thomas, “Fish Stress and Healthy Fishkeeping,” The Aquaria FAQ at http://fins.actwin.com/mirror/

Wedemeyer, G.A. (1996), "Transportation and Handling," in Principles of Salmonid Culture, W. Pennell and B.A. Barton (eds.), pp. 727-758. Cited in Bartelme (2004).

Weitzman, Stanley H., Lisa Palmer, Naercio A. Menezes & John R. Burns (1996), “Maintaining Tropical and Subtropical Forest-Adapted Fishes,” Tropical Fish Hobbyist, June 1996.
Very interesting and helpful, Byron. Thanks for sharing.
 
It is a matter of biology. All species on this planet evolved over time, and what makes each species unique is their DNA. There is no one to "teach" newly-hatched fish how to survive; they know because it is part of their DNA, and this includes how they find their food. As for how the corydoradinae feed, all one has to do is observe these fish in any/all of their habitats.
My point is that putting sand into your mouth is not a natural behavior and therefore has nothing to do with DNA. No species sifts an inert substance of no nutritional value to find food. Filter feeders on sift water.
 

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