Understanding pH and Hardness

[Lawlboom]

I've been reading a lot about pH and have learned a great deal. I'll provide some background before I ask the questions.

From what I know about pH: The measure of the amount of hydrogen Ions in a solution. Higher concentrations result in lower pH and lower concentrations result in higher pH. On a logarithmic scale.

The buffering capacity of water or the resistance to change in pH comes from minerals either abundance or lack of. Higher mineral content = higher pH or Alkaline and lower mineral content = lower pH Acidic.

To bring a solution to neutral 7.0 pH there has be enough of a substance to consume enough hydrogen ions to result in 10^-7 mol/l hydrogen(I'll pretend to know what the number is).

Here's the question: Could all fish be kept in a pH of 7 since it's neutral?

A pH of 8 should be able 10 times more alkaline than a pH of 7. Meaning there are more minerals in the water to buffer the water. So more hydrogen ions.

Is it the hydrogen that causes the problems for the fish or is the presence/lack of minerals.

Does hydrogen/not enough get into the blood stream and cause problems?

I know that fish from generally lower pH will survive in a higher pH. I kept Discus which are naturally found in a very low pH at a pH of 7 and they all grew and seemed happy. Most of the stuff out there is a stable pH is a good pH. Which I stand behind 100% I remember several times hearing people talk at petsmart (when I used to go there back when I first started) about adding crushed coral and what not to mess with their pH and sure enough the first time they did a water change they were carrying back little bags of dead fish for their 14 day refund.

I also know that ammonia and other solutions are much more potent the more alkaline the water is. So is that the other culprit? I know that is why Discus keepers do 50% or greater daily water changes. Conversely a fish of higher pH would tolerate ammonia more at a lower pH.

I'm not sure if I am communicating what I want to know. I want to know what specifically causes the problems for fish. There's a lot of literature on what happens to fish but not how.

One website I read said that Aluminum ions would clog up gills and suffocate fish. Couldn't find anything related.

 

[duanes]

It is possible to keep all fish at a neutral pH of 7, especially bread and butter, aquarium strain, tank bred species. But the question is really, is it always advisable.
This depends on the type fish you are talking about.
If you were to keep wild caught Uaru fernandezyepezi that normally live in waters with a pH of 4, at a pH of 7 in high mineral content water, they may survive, but whether of not they would be healthy is another story.
If you try to keep wild caught rift lake Africans, that normally live in pH 9, in pH 7 they may survive, but would they be healthy, could they readily spawn and produce viable young maybe.
Much has to do with osmotic conditions, because osmotic pressure is different in high mineral content water, and effects cell membranes differently, than the low pH, what almost what might be considered de-ionized water.
And it may not initially or acutely effect the fish kept, but may chronically effect a species if kept in abnormal conditions from what it has (over millions of years) evolved to live in.
How many times have we seen older oscars with HITH?
It may be that years in a tank full of high nitrates may be the major cause, but it also may be the years of stress caused by a combination of elevated nitrates, and out of the norm pH, along with other stressors.
I believe it is always best to keep the fish that match with your water type.

 

[Lawlboom]

Interesting, I'm going to look up the osmosis process in fish.

 

[duanes]

Osmotic pressure works on all cells. That is one of the reasons why you can't keep salt water fish in fresh water, there is a tremendous difference between the osmotic pressure of fresh and salt water. And it is also why you add salt to kill ich, a 3ppt (parts per thousand) salinity is enough osmotic pressure to implode newly hatching ich cells. (sea water is @ 35ppt).
While working as a microbiologist, I was trying to grow certain filtration bacteria on pour plates, when I used DI water for the samples, they would not grow, if I used dechlorinated tap water, they did grow. The lack of osmotic pressure in the DI water would make their cell walls rupture (explode).
I believe this, along with the anti-bacterial quality of tannin, is one of the reasons certain Amazonian species don't do well in much of the hard water we have in states like mine (Wisconsin) where the water comes from the American great lakes, which have a very similar make up to the rift lakes of Africa.

 

[Lawlboom]

Very cool! Thanks for the info!

 

[RD.]

Totally agree with Duane on this. Bacteria that survive in hard water, with higher pH, generally do not exist in the wild where acidic black water species of fish are found. Besides tannins and turpines there are a number of substances found in indigenous plant matter that have antibacterial qualities, such as found in Indian Almond leaves, etc. In years past many spoke of pH shock, which is a misnomer, it is actually a sudden change in TDS (total dissolved solids) that affects the osmoregulation of a fish, and can in some cases cause shock, and even death. I have seen susceptible species of SA fish kept in nitrates as low as 5ppm (but high pH hard water), come down with HITH, while species around them lived out long lives with no such health issues.

FYI ...... discus breeders do large daily water changes, because they feed mammal meat/fat to their fish. I have seen domestic strains grown to large adult sizes with only 1 large weekly water change. The difference, the latter were raised on a much cleaner food. (pellets) These same fish were also raised in hard (200-230 ppm) water, with a high mineral content, and an average pH of 8.0.