What impacts the type of bacteria that grows in an aquarium - carbonate (kh) or ph ?

[jake37]

've been told that blackwater fishes have problem with higher ph in part due to not being able to handle the bacteria that grow in such water relative to acidic water (this ignores the long term impact of kh on softwarer fishes).
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The reason for this question is what happens when you inject co2 for plant growth and the ph goes from 7.2 to 5.8; the carbonate level more or less stays the same but do you kill off the 'beneficial' bacteria each time you lower the ph. The reason for this question is how does 'ph crash' differ from co2 induced acidic water which is generally modest impact on fishes.

 

[Milingu]

've been told that blackwater fishes have problem with higher ph in part due to not being able to handle the bacteria that grow in such water relative to acidic water (this ignores the long term impact of kh on softwarer fishes).

A low pH makes it more difficult or impossible to thrive for certain pathogenic bacteria. Therefore the bacteria load in acidid water tends to be lower which can be beneficial for fish used to a low bacteria load.

The reason for this question is what happens when you inject co2 for plant growth and the ph goes from 7.2 to 5.8; the carbonate level more or less stays the same but do you kill off the 'beneficial' bacteria each time you lower the ph. The reason for this question is how does 'ph crash' differ from co2 induced acidic water which is generally modest impact on fishes.

So called beneficial bacteria are normally necessary to keep you tank cycled (amoniak --> nitrite --> nitrate) but it has no direct effect on fish health.
These bacteria are able to deal with pH swings to a certain degree and do not die immediatly just because the pH goes down a bit. But they die if the pH goes to low. Nitrificiation in extreme acidic water like for example in peat swamps works different respectivley needs different bacteria.

With pH crashes or drops you have to differentiate between 2 types. 1. Nitrification (ammonia --> nitrite) produces acid. And 2. CO2 reacts with the H of H2O and forms acid.
When it comes to a pH crash from the physical point of view there is not much difference between a "normal" nitrifiation induced pH drop and a CO2 induced one. Both mean chemical stress to the fish because they adapt very slow to it. Time plays a huge role here. A fast pH drop is way worse while a slow one might even go unnoticed. Therefore a CO2 induced drop can be even worse than a nitrification induced drop when it happens too fast.

The reason why we see more dead fish by nitrification induced pH drops is that there is often a lot of poisonous ammonia involved and they normaly happen because something went out of controll while CO2 induced pH drops in most cases happen under somewhat controlled circumstanes. But one should be always aware that CO2 is poisonous and fish can suffocate due to much CO2 in their blood.

 

[duanes]

Here are many species of bacteria, and many species within any genus.
There are species within a genus of (for example Aeromonus) that thrive in extremly acidic situations (pH 4 to 7 =/- 0.5, while other species that thrive at a pH of 8.

It is well known, that if you want to grow certain species of bacteria in the lab, manyb are pH dependant, and if you want to grow a certain type, species an agar, a pH type is selected that fits the need of that species. If the agar is too extreme in either direction, some species won't grow
I was a mirobiologist in a drinking water quality lab, and found certain pathogenes did best at a pH of 7.5 tp 8.5. +/_ 0.5., while other species lower pH was needed, acidity in the gut was a determining factor .

Consistency is the key in our tanks for fish health
With (for example Amazonian species, a pH ranging of 4 to 7 (+/-) 0.5), may be a determining factor in preventing certain diseases such as HITH,, for fish evolving in those low pH conditions. (especially if other factors are at play such as nitrate concentration
Whereas
For Central American species evolved to live at a pH of 7.5 to 9, HITH may be of little concern, as long as factors such as high nitrates are also kept within tolerances.
One size (one pH) does not fit all.

 

[duanes]

BTW
I have never used CO2, so feel unqualified to comment.
I do use plants in separate sumps, but in a utilitarian capacity, as nitrate sponges, and with somewhat liimited plant species success
.

 

[jake37]

Here are many species of bacteria, and many species within any genus.
There are species within a genus of (for example Aeromonus) that thrive in extremly acidic situations (pH 4 to 7 =/- 0.5, while other species that thrive at a pH of 8.

It is well known, that if you want to grow certain species of bacteria in the lab, manyb are pH dependant, and if you want to grow a certain type, species an agar, a pH type is selected that fits the need of that species. If the agar is too extreme in either direction, some species won't grow
I was a mirobiologist in a drinking water quality lab, and found certain pathogenes did best at a pH of 7.5 tp 8.5. +/_ 0.5., while other species lower pH was needed, acidity in the gut was a determining factor .

Consistency is the key in our tanks for fish health
With (for example Amazonian species, a pH ranging of 4 to 7 (+/-) 0.5), may be a determining factor in preventing certain diseases such as HITH,, for fish evolving in those low pH conditions. (especially if other factors are at play such as nitrate concentration
Whereas
For Central American species evolved to live at a pH of 7.5 to 9, HITH may be of little concern, as long as factors such as high nitrates are also kept within tolerances.
One size (one pH) does not fit all.

This is useful information but tangent to my question - i should have been more extreme and said if the base ph is 7.8 and the user injects co2 to drive down the ph to 5.8 12 hours a day what impact does this have on the bacteria population and impact on aquatic life.

I know that there is a different between kh level impact on ph and co2 impact on ph in terms of fish response but not if the actual acidic nature is overtly relevant or a by product of either co2 or kh.

 

[Milingu]

Your kh is indirectly relevant for the fish. The higher the kh the more CO2 is needed to drop the pH.
For example for a drop from 7.8 to 5.8 and a kh of 5 you may already reach CO2 levels that are toxic for the fish.

I know that there is a different between kh level impact on ph and co2 impact on ph in terms of fish response but not if the actual acidic nature is overtly relevant or a by product of either co2 or kh.

There is no difference because CO2 and kh are in relation. The CO2 consumes the kh.

Edit: here is a better explanation

15.6.2. KH pH CO2 Relationships in the Aquarium

KH, pH and CO2 form a very complex relationship in the aquarium.

aquariumscience.org

 

[jake37]

There is no difference because CO2 and kh are in relation. The CO2 consumes the kh.

While this statement might be accurate I'm not sure since kh is a chemical composition and if you turn off co2 injection and allow the gas to escape the ph will return and the kh will measure the same as before the injection (i've never measure kh while co2 is being injected so i can't say it impacts that test); but the point is from a chemical perspective i'm not sure of the accuracy of the above statement.