Caliban07
Aquarium Advice Addict
There have been a lot of posts regarding water changes lately. I bet you're as tired as me with this topic however, during one of these discussions a fellow member who was trying to advocate large weekly water changes admitted to not really caring too much for TDS. This led me to believe that they didn't know what TDS was or why it's was important. So I'm going to try and explain this as best I can although I may need some help in places. I'm hoping that new members and fish keepers will read this and maybe think a little bit more about what happens in their tank when TDS is altered and how it may effect our fish.
So I'm going to start by talking about diffusion. Why? It will become apparent. Diffusion as stated by Wikipedia is the net movement of a substance from high concentration to a low concentration. So if we imagine putting a drop of malachite blue in a glass of water the malachite blue will 'diffuse' in to the water until all the water is blue. Shaking the glass or stirring the glass will move the atom/ion/particles around quicker and so the substance will dissolve more quickly.
The reason I mention diffusion is because the next topic I want to talk about is osmosis. As described by Wikipedia again osmosis is the spontaneous net movement of solvent molecules through a semi permeable membrane into a region of higher solute concentration, in the direction that tends to equalise the solute concentrations on the two sides.
In a way, this is the opposite of diffusion because we are now moving from a lower solute concentration to high higher solute concentration but we are going through a semi permeable membrane.
Imagine a fish tank split in two by a semi permeable membrane where only the solvent can pass through and not the solute. For the solvent we will use water and for the solute we will use salt. Imagine the left side is the inside of a cell and the right side is the outside of the cell and the semi permeable membrane is the cell wall. Each side of the cell has a tablespoon of salt. Both the inside of the cell and the outside of the cell are isotonic which means the total molar concentration of dissolved solutes is the same in both of them are a balance is achieved. Perfect right?
Now imagine I add another teaspoon of salt to the outside of the cell wall. Because the concentration of solutes on the outside of the cell wall is greater than the inside water from the water will travel through the membrane to try and achieve balance once more. When this happens the solutes on the outside of the cell become diluted and the concentration of solutes inside the cell now becomes greater than the outside so water moves back through the membrane once more to try and achieve a balance. This will happen a number of times until a balance is achieved and it will happen very quickly creating a small positive and negative pressure as the water passes through the membrane in each direction. The pressure that is require to achieve this balance is known as the osmotic pressure.
Ok still following? Good. Now let's make this relevant to FRESHWATER fish. The reason i emphasise freshwater is because saltwater, although working on the same principle is the opposite.
Freshwater fish are hypertonic to their water environment and therefore, water is continually diffusing into the fish through the gill membranes into blood. Fish have a system that regulates the uptake removal of water to try and achieve a balance between the solutes on both side of the fish. It's the osmoregulatory system. It works in the same principle of our fish tank cell. Water wants to rush in to the fish (semi permeable membrane) because it has a higher salt concentration. How does the fish remove this constant rush of fluids? by urinating mainly. The gills are also permeable to respiratory gases, ammonia waste products, and ions. Therefore, while water moves in towards the higher osmotic pressure of the blood, sodium and chloride ions also diffuse out of the fish, moving down their concentration gradients to the external environment. Freshwater fish must expend energy to regulate this ion loss and fluid uptake.
The continual uptake of water in freshwater species is regulated by the kidneys which continually produces large amounts of dilute urine. Despite the importance of healthy kidneys to help counteract the problem of taking on water, some salts are also lost in the large amounts of urine as well as through the membrane of the gills. Fortunately, the gills are also a site of ion uptake. Special cells in gill lamellae contain sodium and chloride "pumps". These pumps are special enzymes that use energy to move the ions up their concentration gradient to maintain their higher concentration in the body. Thus, osmoregulation is a process that requires the expenditure of much energy on the part of the fish even when they appear to be inactive. This constant expenditure of energy to maintain an osmotic balance is a reason why proper nutrition and low stress levels are important for healthy fish. Damage to the kidneys can be catastrophic for the fish.
So the system in its entirety will always try to achieve this balance of fluid uptake and removal and it is happening on a cellular level. The cells will never really achieve this balance for long as the water chemistry is changing all the time. The system is adapting, controlling and regulating constantly. Having said that, the cells will try to balance the solute content as 'best' they can and around this will be the osmotic pressure. A well fed fish will be happy with the energy demand to keep the balance and. As long as things stay balanced the fish will be stress free.
Let's take a look at a wild caught neon tetra where their environment is very acidic and soft. Soft water fish have a higher osmotic pressure and strong system as the are much more hypertonic to their surroundings.
Let's now put a neon (wild caught) in hard tap water. Even though the fish will always be hypertonic to it's surroundings the ion uptake/loss is much slower than they were used to and the system has to adapt. This uses lots of energy because the difference is so much greater. The neon does not urinate as often so toxins that they might never have been exposed to stay in their body longer which could stress the fish.
On the other hand. Let's put a hard water fish such as a WILD caught swordtail in soft acidic tap water. Water now rushes in to the swordtail much more often than it was used to as the water is void of salts and metals etc. the swordtail has to urinate much more often than normal and overwork the kidneys. Could be a reason these kind of fish suffer from kidney related diseases?
Anyway. The fact that most fish are farm raised means that fish are used to different tap waters depending on their farm. Think of a fishes journey to reach your tank. How many times does this system have to adapt. What is it doing to the fish? How is it effecting them at a physiological level? Is it any wonder lots are sick or have diseases when they reach the LFS?
Think about the TDS in our tank when we change our water. Should we change so much? Is it necessary. What could it do to our fish? Chances are nothing. But i just want you to be aware that it could. I've said it before and I'll say it again. Large water changes are fine if they are done often enough that means the water doesn't alter all that much. Think about fish and how they have to acclimate to change. The things we add to our tanks these days increase the TDS. I just want people to be aware of what it is and what it means to our fish every time we alter their environment. Think about the fish tank cell. Dump a bag if salt on the outside of the cell and the water will rush very quickly to that side resulting in a dehydrated and collapsed cell. Dump the bag in the cell and water will rush in to the cell causing it to Burst. Does rapid fluctuations in TDS damage our fishes cells? Possibly.
A sudden change in osmotic pressure can put great stress on the osmoregulatory system of a fish. This is of great concern when shipping fish to locations with water different from what they're adapted to. The fish arrives under great stress and is not able to regulate any osmotic pressure differences easily. This is one reason why acclimation should be slow. It also explains why treating diseased fish must be done carefully. When putting them in a salt bath, the concentration of salt should be increased gradually.
It is important to understand osmosis and how it affects our fish. It is a vital component for their well-being. Your ability to control problems, safely ship and receive fish and treat diseases will be enhanced if you pay attention to this aspect of their lives.
Thoughts welcome.
Sent from my iPhone using Aquarium Advice
So I'm going to start by talking about diffusion. Why? It will become apparent. Diffusion as stated by Wikipedia is the net movement of a substance from high concentration to a low concentration. So if we imagine putting a drop of malachite blue in a glass of water the malachite blue will 'diffuse' in to the water until all the water is blue. Shaking the glass or stirring the glass will move the atom/ion/particles around quicker and so the substance will dissolve more quickly.
The reason I mention diffusion is because the next topic I want to talk about is osmosis. As described by Wikipedia again osmosis is the spontaneous net movement of solvent molecules through a semi permeable membrane into a region of higher solute concentration, in the direction that tends to equalise the solute concentrations on the two sides.
In a way, this is the opposite of diffusion because we are now moving from a lower solute concentration to high higher solute concentration but we are going through a semi permeable membrane.
Imagine a fish tank split in two by a semi permeable membrane where only the solvent can pass through and not the solute. For the solvent we will use water and for the solute we will use salt. Imagine the left side is the inside of a cell and the right side is the outside of the cell and the semi permeable membrane is the cell wall. Each side of the cell has a tablespoon of salt. Both the inside of the cell and the outside of the cell are isotonic which means the total molar concentration of dissolved solutes is the same in both of them are a balance is achieved. Perfect right?
Now imagine I add another teaspoon of salt to the outside of the cell wall. Because the concentration of solutes on the outside of the cell wall is greater than the inside water from the water will travel through the membrane to try and achieve balance once more. When this happens the solutes on the outside of the cell become diluted and the concentration of solutes inside the cell now becomes greater than the outside so water moves back through the membrane once more to try and achieve a balance. This will happen a number of times until a balance is achieved and it will happen very quickly creating a small positive and negative pressure as the water passes through the membrane in each direction. The pressure that is require to achieve this balance is known as the osmotic pressure.
Ok still following? Good. Now let's make this relevant to FRESHWATER fish. The reason i emphasise freshwater is because saltwater, although working on the same principle is the opposite.
Freshwater fish are hypertonic to their water environment and therefore, water is continually diffusing into the fish through the gill membranes into blood. Fish have a system that regulates the uptake removal of water to try and achieve a balance between the solutes on both side of the fish. It's the osmoregulatory system. It works in the same principle of our fish tank cell. Water wants to rush in to the fish (semi permeable membrane) because it has a higher salt concentration. How does the fish remove this constant rush of fluids? by urinating mainly. The gills are also permeable to respiratory gases, ammonia waste products, and ions. Therefore, while water moves in towards the higher osmotic pressure of the blood, sodium and chloride ions also diffuse out of the fish, moving down their concentration gradients to the external environment. Freshwater fish must expend energy to regulate this ion loss and fluid uptake.
The continual uptake of water in freshwater species is regulated by the kidneys which continually produces large amounts of dilute urine. Despite the importance of healthy kidneys to help counteract the problem of taking on water, some salts are also lost in the large amounts of urine as well as through the membrane of the gills. Fortunately, the gills are also a site of ion uptake. Special cells in gill lamellae contain sodium and chloride "pumps". These pumps are special enzymes that use energy to move the ions up their concentration gradient to maintain their higher concentration in the body. Thus, osmoregulation is a process that requires the expenditure of much energy on the part of the fish even when they appear to be inactive. This constant expenditure of energy to maintain an osmotic balance is a reason why proper nutrition and low stress levels are important for healthy fish. Damage to the kidneys can be catastrophic for the fish.
So the system in its entirety will always try to achieve this balance of fluid uptake and removal and it is happening on a cellular level. The cells will never really achieve this balance for long as the water chemistry is changing all the time. The system is adapting, controlling and regulating constantly. Having said that, the cells will try to balance the solute content as 'best' they can and around this will be the osmotic pressure. A well fed fish will be happy with the energy demand to keep the balance and. As long as things stay balanced the fish will be stress free.
Let's take a look at a wild caught neon tetra where their environment is very acidic and soft. Soft water fish have a higher osmotic pressure and strong system as the are much more hypertonic to their surroundings.
Let's now put a neon (wild caught) in hard tap water. Even though the fish will always be hypertonic to it's surroundings the ion uptake/loss is much slower than they were used to and the system has to adapt. This uses lots of energy because the difference is so much greater. The neon does not urinate as often so toxins that they might never have been exposed to stay in their body longer which could stress the fish.
On the other hand. Let's put a hard water fish such as a WILD caught swordtail in soft acidic tap water. Water now rushes in to the swordtail much more often than it was used to as the water is void of salts and metals etc. the swordtail has to urinate much more often than normal and overwork the kidneys. Could be a reason these kind of fish suffer from kidney related diseases?
Anyway. The fact that most fish are farm raised means that fish are used to different tap waters depending on their farm. Think of a fishes journey to reach your tank. How many times does this system have to adapt. What is it doing to the fish? How is it effecting them at a physiological level? Is it any wonder lots are sick or have diseases when they reach the LFS?
Think about the TDS in our tank when we change our water. Should we change so much? Is it necessary. What could it do to our fish? Chances are nothing. But i just want you to be aware that it could. I've said it before and I'll say it again. Large water changes are fine if they are done often enough that means the water doesn't alter all that much. Think about fish and how they have to acclimate to change. The things we add to our tanks these days increase the TDS. I just want people to be aware of what it is and what it means to our fish every time we alter their environment. Think about the fish tank cell. Dump a bag if salt on the outside of the cell and the water will rush very quickly to that side resulting in a dehydrated and collapsed cell. Dump the bag in the cell and water will rush in to the cell causing it to Burst. Does rapid fluctuations in TDS damage our fishes cells? Possibly.
A sudden change in osmotic pressure can put great stress on the osmoregulatory system of a fish. This is of great concern when shipping fish to locations with water different from what they're adapted to. The fish arrives under great stress and is not able to regulate any osmotic pressure differences easily. This is one reason why acclimation should be slow. It also explains why treating diseased fish must be done carefully. When putting them in a salt bath, the concentration of salt should be increased gradually.
It is important to understand osmosis and how it affects our fish. It is a vital component for their well-being. Your ability to control problems, safely ship and receive fish and treat diseases will be enhanced if you pay attention to this aspect of their lives.
Thoughts welcome.
Sent from my iPhone using Aquarium Advice
