Water change question

[MitchM]

Exactly what mineral levels are you referring to?

eg. Calcium, magnesium, iron, chloride, sodium, sulphate, potassium.

What I am trying to identify is what the limits are of minerals in general that plants and bacteria can process or accumulate so that the mineral levels do not reach values that are harmful to fish.

Is it a better practice to perform regular water changes in order to keep the mineral levels within safe parameters, or are there other methods that can determine when a water change is required?

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[MitchM]

I've had that happen on it's own at my pond. I didn't plan on it but the plants around the pond have grown into the water and cause the water level to drop as they use the water. Looks neat and natural but sometimes I need to pull the roots out and rearrange them to stem the loss of water.

I would encourage further encroachment from native plants.
You local wildlife will thank you.

 

[crsublette]

Does the answer to the question "should I do a water change on my pond" become more critical if the pond is located in a dry or humid environment, or if the source water is hard or soft?

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Depends on what you are doing to the water... I know folk want to try to claim a plastic lined hole in the ground is "all natural" thus needs little or near zero maintenance... if you look at nature (in my opinion as far as I have seen)... there is no "naturally occurring" 2,000 gallon healthy ponds with fish (that are still alive)...

"Should I do a water change?" depends on... what are your goals? where is your pond located? what are you doing to the pond? what are you not doing to the pond? what is Mother Nature doing to your pond? etc etc...

In integrated multi-trophic recirculating aquaculture (IMTRA) systems (i.e., an agriculture industry involving watergardens on steroids, referred to as aquaponics in the hobby arena), they never do any purposeful water changes since they have the proper filtration involved and control their source water best they can... These fellas also have a balance "plant to fish" and don't do anything that screws up the "ecosystem".

Salts such as sodium and chlorides (etc etc) can become a problem after some years, even sooner if the human or Mother Nature or water runoff (or etc etc) is supplementing the pond water. ... However... If you are in an area that receives rain, then this added water from a heavy rain can implement a decent enough water change... So... even for salts like sodiums and chlorides... you might not need to do a water changed... by the ways, takes ALOT of chlorides to incur any type of phototoxicity in plants or fish ((personally, I never seen "too much" chlorides happen even within aquaponics))

Problem the most overlooked variable involving water changes is water temperature... a quick change in water temperature can shock fish and, if change is big enough, can result to allowing secondary ailments occur. This is why I think nobody should ever do a water change during winter... If your pond water is 45*F and your source water is 60*F, then this possible could mean bad news depending on quick the change is...

I have hard, alkaline water... and I know exactly what I am doing (and not doing) to my pond... so I implement a type of "flow through" water change... that where something like, every hour, 5~10% of the pond's water is emptied to water my trees or flower beds or little garden plot and then adding 10% freshwater at the same time...

I would say NO to water changes... unless... you know exactly why are you doing for a good reason rather than "should, just because it seems healthier"... this is especially true if your water is quite soft and acidic.... not as a big deal with hard, alkaline water (assuming you know what is in your source water).

 

[crsublette]

I've had that happen on it's own at my pond. I didn't plan on it but the plants around the pond have grown into the water and cause the water level to drop as they use the water. Looks neat and natural but sometimes I need to pull the roots out and rearrange them to stem the loss of water.

Good example of a natural water change.

Truly astounding how much water plant's use for evapotranspiration and to circulate nutrients within the plant. Plants can also reduce salt levels within the water. Plants also help to keep the water clear through their root exudates and agglutinins (a coagulation excretion).

More plants the better. ... and the plants do not have to be inside the pond... can simply be a pump that pushes water from the pond into a big terrestrial grow containers, which gravity drain back into the pond (although this can discolor your water)...

 

[Meyer Jordan]

What I am trying to identify is what the limits are of minerals in general that plants and bacteria can process or accumulate so that the mineral levels do not reach values that are harmful to fish.

You can start here for the toxicity levels.
http://water.epa.gov/scitech/swguid...qlife/upload/2009_01_13_criteria_goldbook.pdf

In addition to knowing the levels, you need to know at what rate the individual minerals are being introduced to the pond. This means testing which could get expensive.

Keep in mind that, with a few exceptions, most minerals and compounds are present in ionic form, which means that they readily react with other ions to form more stable molecules. Add to this the fact that, here again, most minerals are toxic only in the ionic form. Man-made chemicals are a completely different, in that half-life, is the prime consideration.
In Nature, many bodies of water are closed-system yet continue to support aquatic life year after year. Even in those bodies of water that may be flow-through, the water entering the particular pond or lake is often more highly polluted than the outflow, yet these also continue to support aquatic life year after year.
Nature provides control of toxic levels of minerals and compounds through disassociation and reassociation into inert precipitates or other relatively stable compounds or through assimilation/oxidation by various aquatic organisms.
Unless potentially toxic material is introduced by human means, the chance of any reaching toxic levels naturally is miniscule.

 

[crsublette]

In Nature, many bodies of water are closed-system yet continue to support aquatic life year after year. Even in those bodies of water that may be flow-through, the water entering the particular pond or lake is often more highly polluted than the outflow, yet these also continue to support aquatic life year after year.
Nature provides control of toxic levels of minerals and compounds through disassociation and reassociation into inert precipitates or other relatively stable compounds or through assimilation/oxidation by various aquatic organisms.
Unless potentially toxic material is introduced by human means, the chance of any reaching toxic levels naturally is miniscule.

I would bet money that the biological diversity and density, among other mechanizations, are exponentially greater in those bodies of water versus the typical backyard pond environment and will take a very long time for ours to emulate the diverse ecosystem of those larger bodies of water... and then there is that "shock" differential... much easier to cause ill affects (distorting the ecosystem) in smaller bodies of water versus larger bodies of water...

Lets not forget the ugly side of Nature... even in those large bodies of water, bays, small enclaves... there are areas where you would not want to do any skinny dipping.

 

[Meyer Jordan]

I would bet money that the biological diversity and density, among other mechanizations, are exponentially greater in those bodies of water versus the typical backyard pond environment and will take a very long time for ours to emulate the diverse ecosystem of those larger bodies of water... and then there is that "shock" differential... much easier to cause ill affects (distorting the ecosystem) in smaller bodies of water versus larger bodies of water...

Lets not forget the ugly side of Nature... even in those large bodies of water, bays, small enclaves... there are areas where you would not want to do any skinny dipping.

You would be correct, but also the diversity and density of mineral content would be greater because a natural body of water draws from a large watershed, a garden pond has virtually NO watershed.
The subject of pathogen levels is a subject for a separate discussion, this is about mineral content.

 

[MitchM]

Hey Charles.
I absolutely agree with you and Meyer that evapotranspiration is an important consideration.
BUT, not all evapotranspiration is equal.

What are the differences of evapotranspiration between a tropical elephant ear plant and a coniferous spruce tree? ( as extreme examples) That seems to me to be just as important as relative humidity.
And what happens to the minerals? Do they accumulate in the plant tissue that then needs to be harvested and then taken away from the pond?

Meyer, how are natural bodies of water closed system, except for the Dead Sea?
Are not most bodies of water "flow through" that sustain mineral levels relative to the surrounding environment?

 

[Meyer Jordan]

Hey Charles.
I absolutely agree with you and Meyer that evapotranspiration is an important consideration.
BUT, not all evapotranspiration is equal.

What are the differences of evapotranspiration between a tropical elephant ear plant and a coniferous spruce tree? ( as extreme examples) That seems to me to be just as important as relative humidity.
And what happens to the minerals? Do they accumulate in the plant tissue that then needs to be harvested and then taken away from the pond?

Meyer, how are natural bodies of water closed system, except for the Dead Sea?
Are not most bodies of water "flow through" that sustain mineral levels relative to the surrounding environment?

Many natural bodies of water are not flow-trough. The 'Kettle' ponds are the first that come to mind.

See: https://en.wikipedia.org/wiki/Endorheic_basin

 

[MitchM]

I'm not familiar with the Kettle ponds, I'll have to look those up. Thanks.

 

[peter hillman]

I do partial water changes. When I do they're done in the morning when the pond temp is as close to the 'hose' temp as possible. Then fill in stages to let the temps adjust. Agreed major temp changes are the worst for fish. Since I joined this forum I've spent much more time at the pond and thus the fish ate more than probably ever prompting yesterdays AM change. The plants had lots of new growth in the water while the part that stays on land started to yellow with the season. Also, that familiar overworked filter stench confirmed foul water. My fish are no water snobs, but I still care about their environment. And they're going on a diet. I stopped using any de-chlorinator years ago.

 

[addy1]

I add water, never change water, unless it rains really hard. Ours is well, soft and acidic.