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Low ph tank with modest gh ?

anewbie

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I know that there are species (many) species that prefer low ph to breed with success. And people have 'black water' tank to support their environment; but I always associated blackwater with very soft water (0-3 gh). Can you have a much higher gh (6-8) without adverse effect on the fishes. While this would not be 'black water' it would be more plant friendly.
 

MacZ

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GH and pH have no direct connection. KH is the value you would have to look after.

Problem ist the combination of pH and GH in breeding. Extremely low calcium and magnesium plus low pH make for a very bacteria-hostile environment. That's the key thing and why blackwater fishes eggs won't hatch above a certain hardness/pH.

For many of these species these values are hard to measure really reliably. Many pH drip tests don't work under a certain KH and so most work with TDS/EC readings instead.
 

anewbie

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GH and pH have no direct connection. KH is the value you would have to look after.

Problem ist the combination of pH and GH in breeding. Extremely low calcium and magnesium plus low pH make for a very bacteria-hostile environment. That's the key thing and why blackwater fishes eggs won't hatch above a certain hardness/pH.

For many of these species these values are hard to measure really reliably. Many pH drip tests don't work under a certain KH and so most work with TDS/EC readings instead.
I realize there is no relationship between gh and ph but gh is hardness right? Most of the lit talk about these fishes doing better with soft acidic water; my question is do they do well with not super soft but acidic water ?
 

anewbie

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It depends on the species. Generally speaking, blackwater fish will live and spawn fine in harder water, but the egg casings may harden and not hatch in those conditions.
Ok so i can start with modest gh (3-4) and then lower it as needed i guess. My presumption is plants will do better with the higher gh despite the low ph (and changes in chemistry due to lower ph but perhaps my assumption is false).
 

Ben Rhau

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A lot of them do, but plenty of plants can thrive in soft water. Surface floaters, mosses, anubias, ferns, etc. I gave up on trying to grow more nutrient-hungry plants in apisto tanks. The conditions (chemistry and flow) just aren’t compatible.
 

MacZ

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Germany
I realize there is no relationship between gh and ph but gh is hardness right? Most of the lit talk about these fishes doing better with soft acidic water; my question is do they do well with not super soft but acidic water ?
Well for the H in KH also stands for hardness. German "Karbonathärte" ( = carbonate hardness = alkalinity). So "soft acidic" usually means devoid of both GH and KH.

Blackwater fish have a tendency to do just "meh" in harder water. Breeding is most often not going to happen and if it still does often the successrate is low. I don't know anymore in which book I read it, but cardinal tetras for example become mostly sterile when grown out in too hard water. There are reports about softwater fish (it's more than just blackwater) also developing a tendency to kidney problems and of course have higher susceptability to bacterial infection.

I agree with Ben about the plants: Floaters and anything that can grow above the waterline is going to do well with just a minimum of liguid full-spectrum fertilizer, even in 100% RO.

My presumption is plants will do better with the higher gh despite the low ph (and changes in chemistry due to lower ph but perhaps my assumption is false).
The idea is not wrong, but you are probably a bit too careful. Not all, but many plants can thrive with less than 1°GH.
 

MacZ

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Not all, but many plants can thrive with less than 1°GH.
I just realized: In my tank it helped to also choose almost only South American species known from flooded forests and lakes. (exceptions Pistia and Salvinia)
 

anewbie

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I know which plants i wnat to grow just not sure if they will grow. Anyway this project is about a year out due to delays - but i think it will be more oriented to low ph than 'blackwater'. Just wish i coudl experiment before setting up the tank - maybe i could buy some ro water and put in a 5 gallon - not sure i have room for another 5.
 

MacZ

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Germany
more oriented to low ph than 'blackwater'
Goes hand in hand. Look at the water parameters in both articles, it should be self-explanatory, I don't have the capacity right now to say what I want to say about this.


You want low pH you have to go down with the conductivity at some point, even though GH has almost nothing to do with pH. I think what you might try aiming at could be clearwater.
 

anewbie

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Goes hand in hand. Look at the water parameters in both articles, it should be self-explanatory, I don't have the capacity right now to say what I want to say about this.


You want low pH you have to go down with the conductivity at some point, even though GH has almost nothing to do with pH. I think what you might try aiming at could be clearwater.
This is the aspect that I'm focused on:
Comparison between clear and black waters[edit]
Blackwater rivers resemble clearwater rivers in having a low conductivity and relatively low levels of dissolved solids, but clearwater rivers have water that often only is somewhat acidic (typical pH ~6.5)[3].

The wiki page states the primary difference is ph; but there is no reason why I can't have 'clearwater' that is much lower ph and higher in mineral content. It might not match the fish native habitat but that might not matter as long as it meets their health and breeding needs. I can of course explore breeding but i don't have a good way to explore overall health.
 

MacZ

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Germany
there is no reason why I can't have 'clearwater' that is much lower ph and higher in mineral content.
The reason is called chemistry. That's what I meant by "self-explanatory". You won't get that far down without using things like hydrochloric or sulfuric acid. pH measures H+ ions. Those have to come from somewhere. In blackwater it's the tannic and humic substances. Clearwater usually doesn't have such low pH as blackwater because it lacks the vast amounts that are solved in blackwater. So to get further down than let's say 6.5 (which is only slightly acidic in my book) you will need a source of acidity. This is not yet low pH.
Blackwater is stable in low pH because humic substances buffer the pH between 4 and 6. You want to get to a certain low pH without these substances you risk a pH crash. Except when you add carbonates back in, in which case you could just stick to tap, because this will block you from getting pH down at some point.
A pH-crash is rare and usually happens only under two circumstances: Either no buffer in the water at all or slowly regression of buffer levels due to accumulation of nitric acid (high levels of nitrates) in unmaintained tanks.
 
Last edited:

Ben Rhau

Apisto Club
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566
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San Francisco
It sounds like the OP just wants to add more calcium and magnesium ions to blackwater. At that point, I think you’re trying to thread the needle of keeping the conductivity just low enough for your fish, with a GH high enough for your chosen plants. Whether that works depends on which fish and which plants.

Another thing to consider is that the more nutrient hungry plants need good gas exchange to thrive, which may require more water flow than is typical for an apisto tank. You can increase the water flow, which is also not native. Most apisto keepers don’t do that, but I think Darrel has done it with success. You probably need the plants so dense that they baffle the flow.
 

MacZ

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2,959
Location
Germany
It sounds like the OP just wants to add more calcium and magnesium ions to blackwater. At that point, I think you’re trying to thread the needle of keeping the conductivity just low enough for your fish, with a GH high enough for your chosen plants. Whether that works depends on which fish and which plants.
Agree, which is not easy really. Threading a needle is quite a good metaphor for this. In my experience with the right plants it's possible, but GH stays below detection.

Another thing to consider is that the more nutrient hungry plants need good gas exchange to thrive, which may require more water flow than is typical for an apisto tank. You can increase the water flow, which is also not native. Most apisto keepers don’t do that, but I think Darrel has done it with success. You probably need the plants so dense that they baffle the flow.
Agree, too.
 

anewbie

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1,366
Hum. I think one thing I will do is grow plants that can handle both emersed and submersed at the same time and only fill the tank 1/2 way so they have plenty of vertical space above the water line.
 

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