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Absolute beginner to black water tanks

Popsic

New Member
Messages
11
Hi all,

I’ve been in the fish keeping hobby for a while (just over a year) and I’ve tried different setups like walstad, but I’d really like to try a black water tank.

Forgetting the chemistry lesson, which I know is important but not wanting to get way in over my head too early, what is actually required to setup a black water tank?

Do I need a RO system?

I’m just trying to gauge how expensive it would be to setup my first black water tank.

My tap water is 7.6 pH so I know I’d have to do something to bring that down, but again I’m not sure what.

Thanks in advance.
 

MacZ

Well-Known Member
Messages
1,740
Location
Germany
Forgetting the chemistry lesson, which I know is important but not wanting to get way in over my head too early, what is actually required to setup a black water tank?
I can only stress: If you don't have the chemistry basics, more than a faux blackwater (= tap tinted by humic substances) isn't going to happen. A condensed Q&A for the basics you can find here.

Do I need a RO system?
For "true" blackwater you will need either RO, DI, distilled or rainwater. Or tapwater as soft as in the scottish highlands. No way past that.

I’m just trying to gauge how expensive it would be to setup my first black water tank.
A RO system suitable for a 100-150l tank is available for 50-70 €/$/£. In comparison to buying distilled water a unit usually pays off after 1-3 months. A DI stage for the system is not necessary. Rainwater is free though.
Alder cones and catappa leaves go for 5-10,- per decently sized package of second quality (cones: 500g, leaves: 100pc.) from specialized online vendors. Or go and collect yourself in autmn. Almost any brown deciduous leaves will do.
Unfertilized white peat is in many places available for 20,- for a 50kg bag. And that will last you some years. Although I don't endorse it as it's not sustainable.
Tank, light, heater and filter can be all standard. So in the end you can do a blackwater tank even cheaper than a "normal" planted tank with CO2 injection.
If you already have more than one tank and spares (e.g. an old unused filter or a light) or even a free unstocked tank, you could pull off a blackwater setup for less than 100 bucks. (And yes, I have experience with low budget in the hobby.)

My tap water is 7.6 pH so I know I’d have to do something to bring that down, but again I’m not sure what.
Let it sit for 24h and test again. Often the pH goes down a bit after it's out of the tap.
Generally though KH (carbonate hardness/alkalinity) is the measurable parameter that determines pH. You can test it, but frankly... 7.6 tells me your water is very likely not suitable for blackwater. So it stands, RO or the like are necessary.
In already soft water (KH below 5°) you could use peat, but otherwise adding stuff isn't helping to make water softer and more acidic. Only removal.
(And I know there's the option of using acids but that doesn't make for blackwater as it raises Electric Conductivity, which has to be low).
 
Last edited:

Popsic

New Member
Messages
11
Thanks @MacZ - that was all very helpful.

I can only stress: If you don't have the chemistry basics, more than a faux blackwater (= tap tinted by humic substances) isn't going to happen. A condensed Q&A for the basics you can find here.
For "true" blackwater you will need either RO, DI, distilled or rainwater. Or tapwater as soft as in the scottish highlands. No way past that.
The one thing that stood out for me in the article you linked was this bit: "Pretreating water with an RO unit can, depending on its efficiency, use quite large amounts of water with RO to wastewater ratios of up to 1:5! So if you live in areas with regular droughts, high water hardness and/or high prices on tapwater you might want to overthink this."

I think that, coupled with the fact that my water isn't really suitable without such a unit, means that black water isn't really an adventure I should embark on (at least, not right now).

A RO system suitable for a 100-150l tank is available for 50-70 €/$/£. In comparison to buying distilled water a unit usually pays off after 1-3 months. A DI stage for the system is not necessary. Rainwater is free though.
Alder cones and catappa leaves go for 5-10,- per decently sized package of second quality (cones: 500g, leaves: 100pc.) from specialized online vendors. Or go and collect yourself in autmn. Almost any brown deciduous leaves will do.
Unfertilized white peat is in many places available for 20,- for a 50kg bag. And that will last you some years. Although I don't endorse it as it's not sustainable.
Tank, light, heater and filter can be all standard. So in the end you can do a blackwater tank even cheaper than a "normal" planted tank with CO2 injection.
If you already have more than one tank and spares (e.g. an old unused filter or a light) or even a free unstocked tank, you could pull off a blackwater setup for less than 100 bucks. (And yes, I have experience with low budget in the hobby.)
Thank you :)
Let it sit for 24h and test again. Often the pH goes down a bit after it's out of the tap.
Generally though KH (carbonate hardness/alkalinity) is the measurable parameter that determines pH. You can test it, but frankly... 7.6 tells me your water is very likely not suitable for blackwater. So it stands, RO or the like are necessary.
In already soft water (KH below 5°) you could use peat, but otherwise adding stuff isn't helping to make water softer and more acidic. Only removal.
(And I know there's the option of using acids but that doesn't make for blackwater as it raises Electric Conductivity, which has to be low).

As a follow-up question... Is it at least beneficial to fish (currently thinking of a tank with two Apistogrammas - one Cacatuoides and one Macmasteri) to adopt faux blackwater?

Like, if I picked up some IAL/Oak leaves from a local forest, or some alder cones (if there are any around me, I don't know) and added quite a few of them to the tank to "blacken" the water - that would still release tannins I believe? Would that still be beneficial to the fish, or is it more aesthetics for the fish keeper?

Would the leaves lower the pH?
 

MacZ

Well-Known Member
Messages
1,740
Location
Germany
I think that, coupled with the fact that my water isn't really suitable without such a unit, means that black water isn't really an adventure I should embark on (at least, not right now).
Understandable.

As a follow-up question... Is it at least beneficial to fish (currently thinking of a tank with two Apistogrammas - one Cacatuoides and one Macmasteri) to adopt faux blackwater?
Humic substances are very much useful. Also both species are not blackwater species. At best you can do clearwater (almost as soft, far less acidic).

Like, if I picked up some IAL/Oak leaves from a local forest, or some alder cones (if there are any around me, I don't know) and added quite a few of them to the tank to "blacken" the water - that would still release tannins I believe? Would that still be beneficial to the fish, or is it more aesthetics for the fish keeper?
Well, if you have oaks, you won't find IALs, as these are (sub-)tropical trees.
Anyhow, no, it's not just aesthetics, quite the opposite. beneficial biofilms and infusoria will grow on botanicals nonetheless and are a welcome enrichment.

Would the leaves lower the pH?
No, or at least not significantly. If your KH is higher than 1-2°, botanicals have no real effect on pH.
 

Popsic

New Member
Messages
11
Humic substances are very much useful. Also both species are not blackwater species. At best you can do clearwater (almost as soft, far less acidic).
Awesome, thank you :) I had thought those species prefer blackwater, but I was obviously wrong!
Well, if you have oaks, you won't find IALs, as these are (sub-)tropical trees.
Anyhow, no, it's not just aesthetics, quite the opposite. beneficial biofilms and infusoria will grow on botanicals nonetheless and are a welcome enrichment.
Ahh ok! I'll keep my eye out for Oak leaves and alder cones then :)

Slightly tangental question - is there an amount of time I should leave the leaves in the tank for? I don't have shrimp, so they are unlikely to get eaten, so presumably there becomes a time they aren't providing any use and should be removed to keep the tank clean?

Or is it not an exact science and just should be removed when they start deteriorating?

No, or at least not significantly. If your KH is higher than 1-2°, botanicals have no real effect on pH.

Thanks for confirming :)
 

MacZ

Well-Known Member
Messages
1,740
Location
Germany
I had thought those species prefer blackwater, but I was obviously wrong!
Some populations do, as Mike often mentions, but let's face it, the likelihood you have a wild caught A. cacatuoides AND from one of these locations is low.

Slightly tangental question - is there an amount of time I should leave the leaves in the tank for? I don't have shrimp, so they are unlikely to get eaten, so presumably there becomes a time they aren't providing any use and should be removed to keep the tank clean?
Until they are decomposed to mulm. A good mulm layer is helping keeping the whole system stable.

I prefer a good leaf litter bed to a clean open substrate. And your fish will very likely too.

Or is it not an exact science and just should be removed when they start deteriorating?
It is not an exact science, sadly, as we can only observe the processes but not exactly control them. But the deterioration is what we want. It releases more humic acids and grows colonies of microorganisms that play important rolls in the food web and the cycle.
 

Popsic

New Member
Messages
11
Some populations do, as Mike often mentions, but let's face it, the likelihood you have a wild caught A. cacatuoides AND from one of these locations is low.
Ah ok, that makes sense! Thanks! Yeah, it's very unlikely they are wild caught.
Until they are decomposed to mulm. A good mulm layer is helping keeping the whole system stable.

I prefer a good leaf litter bed to a clean open substrate. And your fish will very likely too.
Ahh ok, so basically just leave it until it's sludge and then remove it?

I'll have to see if I can find a way of making the leaves stay on the bottom then :) they always seem to just float around for me haha.
It is not an exact science, sadly, as we can only observe the processes but not exactly control them. But the deterioration is what we want. It releases more humic acids and grows colonies of microorganisms that play important rolls in the food web and the cycle.

Thanks for explaining :)

Really appreciate all the replies @MacZ !
 

MacZ

Well-Known Member
Messages
1,740
Location
Germany
In the end it should look like this:
IMG_20220915_180824.jpg
IMG_20220915_180836.jpg

IMG_20220915_180926.jpg

IMG_20220915_181833.jpg
 

Popsic

New Member
Messages
11
Do you do anything special to help the leaves sink on the bottom like that, or do you just let them float until they sink?
 

MacZ

Well-Known Member
Messages
1,740
Location
Germany
I pour (near) boiling water over and let them steep. When it cooled down I add the leaves and the brew. They sink immediately.
 

Popsic

New Member
Messages
11
Small update - After my WC today, I added six IAL (three pre-boiled and laying on the substrate) and three just rinsed and floating.

Decided to make it nice and dark, so added in more leaves than I probably needed. Hoping it will darken over the next few days.
 

MacZ

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Messages
1,740
Location
Germany
Keep an airstone ready. The first few days after adding the stuff is being colonized by microorganisms. That process takes a lot of oxygen, so an acute oxygen deficiency is possible.
 

Popsic

New Member
Messages
11
Keep an airstone ready. The first few days after adding the stuff is being colonized by microorganisms. That process takes a lot of oxygen, so an acute oxygen deficiency is possible.

Ah, ok! Fascinating stuff! I'm almost certain I've got a spare air-pump somewhere!

Is the oxygen deficiency a higher risk because I put more leaves in, or will it be a consideration any/every time I add leaves?
 

MacZ

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Messages
1,740
Location
Germany
Is the oxygen deficiency a higher risk because I put more leaves in, or will it be a consideration any/every time I add leaves?
General thing, but the more the likelier.

Maybe read the latest entry on the blog "The Tint" on tanninaquatics. I can generally recommend that blog, as it's not a typical advertorial one might expect, but a quite honest blog on the whole topic.
 

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