blackwater tank cycling?

[Ben Rhau]

So the acid will raise tds ? Will it take water changes to remove the tds increase by acid ? My ec pen has a 500 and 700 choice but i think ec was around 8 (tds 26).

Of course, strong acids are ions, but if you're starting with RO water to begin with, you don't need to add much acid, so the contribution to conductivity is negligible. If you started with a very high KH, you would need to add a lot of acid to neutralize it, driving up the conductivity even further. Starting with RODI, I'm able to keep the EC below 25 and the pH below 5.

I'm not sure how you're calculating TDS, but with an EC of 8, TDS = 8 * 0.64 = 5.

The problem with "strong acids" is that they don't add any buffering, they disassociate fully, whereas "weak acids" don't and they have two disassociation constants. Personally I'd keep well away from both concentrated (conc.) acids and strong acids. Have a look at <"citric acid"> and <"All the leaves are brown">

Yes, I understand that strong acids do not buffer at low pH. However, the lower the pH, the less acid you need to neutralize the residual carbonate. The pH will always drift toward 5.5 (in my case) but the kinetics are such that, at least in my aquariums, I can keep it a range below 5 until the next water change (when I add more acid). The EC remains below 25.

Citric acid can work, but as Regani notes in that thread, it degrades over time, and he eventually shifted to mixing it with HCl. The advantage of the citric acid component is that it lowers conductivity further by complexing divalent cations. Is that necessary? In my case, no. I also don't know by how much it reduces.

So you are saying (i think) ignore ph and just be happy tds is 25 ec is 8 and it will all work out ?

It depends on the species. I've never kept a very low pH tank for an apisto species, but I've also never kept true blackwater apistos. I do maintain low pH tanks for wild caught Parosphromemus. The guidance is that the immune systems of these animals, through natural selection, have lost the ability to defend against pathogens that thrive at higher pH. So it's a prophylactic measure to prevent them from seeing those organisms. Is that necessary? I don't know for sure, but some very experienced (and academic) keepers strongly recommend it. Given the scarcity of these animals, I'm not going to experiment with it myself.

I would determine what's actually needed for your species, based on the literature and breeding reports.

Have you ever considered Fulvic Acid, Darrel?

I've not seen a liquid fulvic acid that is low in pH. I believe its solubility in water is poor, so NaOH or KOH are added to keep it in solution. So, beneficial for some reasons, but ineffective for lowering pH.

-B

 

[anewbie]

@Ben Rhau I'm not calculating tds the meter i have display that value (I actually have two different tds meters and they both show pretty much the same value). One is the aspera ph pen (i don't trust the ph part) and the other is one of those yellow/grey cheap tds pens.
-
The species will be wild caught WC Bitaeniata Shishita - so my guess is they are not as demanding as some species but still....

 

[dw1305]

Hi all,

Of course, strong acids are ions, but if you're starting with RO water to begin with, you don't need to add much acid, so the contribution to conductivity is negligible. If you started with a very high KH, you would need to add a lot of acid to neutralize it, driving up the conductivity even further. Starting with RODI, I'm able to keep the EC below 25 and the pH below 5.....

The pH will always drift toward 5.5 (in my case) but the kinetics are such that, at least in my aquariums, I can keep it a range below 5 until the next water change (when I add more acid). The EC remains below 25.

Citric acid can work, but as Regani notes in that thread, it degrades over time, and he eventually shifted to mixing it with HCl. The advantage of the citric acid component is that it lowers conductivity further by complexing divalent cations. Is that necessary? In my case, no.

That is absolutely fine, you know what you are doing. It is partially why I like conductivity as a reading, at the same time as not telling you anything specific, it actually tells you a lot.

I think quite a lot of members do the same, you can't search for HCl on the forum, but <"muriatic"> or <"hydrochloric acid"> will bring up plenty of results. Personally I'm going to carry on with the rain water and botanicals, but it does preclude me from keeping real black-water fish.

cheers Darrel

 

[martin_c]

hey @all,
i don’t mean to high jack this interesting thread.
Since it became about maintaining large real black water tanks, i'd like to bring to the table another way of maintaining those, which i'm practising with my 450L tank for about ~1 year.

In other forums i wouldn't tell this, because i'd get accused of laziness or whatever, but this forum seems to be more open minded.

Instead of water changes i do what i call a reset of salts. It's similar to what's known (at least in germany) as "indirect water change". I do it like this:
- my water is constantly at ph ~4.5 and 15-20µs (ec stays there due to heavy external planting)
- when "water changing", i first increase the tank water with a ph-neutral mineral salt to ~45µs
- then i attach my DI-Unit directly to the tank, until it's back at 15µs
- there is no threat of too much co2 because there's not enough carbonate getting cracked to release dangerous amounts of co2. To my surprise ph doesn't even decline while doing this.
- there is no threat of filthifying the resin of the DI-Unit, because i'm using 1-way mixed bed resin, which is ok because this way resin lasts 10x as long compared to using it on tap water.
- there's no heating up large amounts of cold water
- there is no stress for fish
- at PH of ~4.5 bacteria / pathogens aren't an issue anyway
- i also add some activated carbon to the DI-Unit, not sure if that's necessary though..

The reasons why i decided to do this:
- regular water changes used to put my pair of heckel discus into a life crisis for 2 days (especially if some decorational root had collapsed while water changing)
- with my osmosis system water changes took 2 days, because i couldn't store enough osmosis water for a large water change.

I thought it's a hobby so why not just try things, and so far i love it, all fish (and plants) are thriving (you can barely detect the breathing movement of the heckels).

I'm open to criticism though

 

[Ben Rhau]

Not a criticism, I just don't quite understand... You add salt, and then remove it through DI. What is the net effect on the water?

 

[martin_c]

Not a criticism, I just don't quite understand... You add salt, and then remove it through DI. What is the net effect on the water?

I reset the composition of solved salts from <i dont really know what> to <what the backside of sera mineral salt says>. At least 66% of it.
Oh, and theoretically i could do it the other way around, first decrease it to 5 and then increase to 15, but that seems risky.

 

[Ben Rhau]

Ah, right. It also removes nitrate. I remember I heard of a hobbyist with a smaller tank who would shake his water in DI resin beads in order to clean it instead of making new water. Same idea.

In my case, I wouldn't replenish the salts, since my fish natively live in practically deionized water. But it sounds like it works for your case!

 

[anewbie]

I'm sorry i've gotten lost; my current ph is 6.64; what is the highest ph that i should consider acceptable for blackwater fishes - 5.5? 6.0? (I added more accurate monitoring of ph).

 

[MacZ]

I'm sorry i've gotten lost; my current ph is 6.64; what is the highest ph that i should consider acceptable for blackwater fishes - 5.5? 6.0? (I added more accurate monitoring of ph).

5 to 6, as long as the conductivity stays low.

 

[MacZ]

hey @all,
i don’t mean to high jack this interesting thread.
Since it became about maintaining large real black water tanks, i'd like to bring to the table another way of maintaining those, which i'm practising with my 450L tank for about ~1 year.

In other forums i wouldn't tell this, because i'd get accused of laziness or whatever, but this forum seems to be more open minded.

Instead of water changes i do what i call a reset of salts. It's similar to what's known (at least in germany) as "indirect water change". I do it like this:
- my water is constantly at ph ~4.5 and 15-20µs (ec stays there due to heavy external planting)
- when "water changing", i first increase the tank water with a ph-neutral mineral salt to ~45µs
- then i attach my DI-Unit directly to the tank, until it's back at 15µs
- there is no threat of too much co2 because there's not enough carbonate getting cracked to release dangerous amounts of co2. To my surprise ph doesn't even decline while doing this.
- there is no threat of filthifying the resin of the DI-Unit, because i'm using 1-way mixed bed resin, which is ok because this way resin lasts 10x as long compared to using it on tap water.
- there's no heating up large amounts of cold water
- there is no stress for fish
- at PH of ~4.5 bacteria / pathogens aren't an issue anyway
- i also add some activated carbon to the DI-Unit, not sure if that's necessary though..

The reasons why i decided to do this:
- regular water changes used to put my pair of heckel discus into a life crisis for 2 days (especially if some decorational root had collapsed while water changing)
- with my osmosis system water changes took 2 days, because i couldn't store enough osmosis water for a large water change.

I thought it's a hobby so why not just try things, and so far i love it, all fish (and plants) are thriving (you can barely detect the breathing movement of the heckels).

I'm open to criticism though

I have just one point of critique, but that's due to my mindset ("least effort to maximum effect"): I don't get the amount of work and steps.
What I especially don't get is using mineral salts when the goal is minimum conductivity. Yes I get the point of making sure all of the singular elements are replenished, but as Ben mentioned correctly: The fish are basically used to completely deionized waters. All that extra work and extra steps seem so redundant and a bit wasteful.

A well seasoned tank based on low conductivity water can go with minimum effort.
My tank is a bit of a special example:
Base water is RO with a conductivity of 10microS/cm, I only add humic substances and botanicals. For a while I added minimum amounts of liquid ferts but that has faded out by now. On top I have about 15 meters of Epipremnum and several thickets of Hydrocotyle for plant filtration plus floaters. And as there is a lot of evaporation I refill 2-3 liters a day with pure RO. I haven't done a waterchange in months. But this only works due to the plants and the water I use. TDS are at a constant 30, pH is constant between 5 and 5.5.
Would I add a DI stage to my RO unit I could push it down to your values. so... yeah... I understand your approach, just can't understand the effort.

 

[dw1305]

Hi all,

I'm sorry i've gotten lost; my current ph is 6.64; what is the highest ph that i should consider acceptable for blackwater fishes - 5.5? 6.0?

I agree with @MacZ , probably lower, but if it is a planted tank? Then the plants will remove net CO2 from the water during photosynthesis and the pH will rise.

Plants (and photosynthesis) are a good thing for tank health, and you haven't actually increased the alkalinity level, you've just mimicked an atmosphere poorer in CO2. If you can lower the pH (with acids, fulvic and humic for me) so that it remains below pH 7 during photosynthesis? You are in a good place for black water fish.

The same applies outside of the photoperiod, you can drastically reduce pH by letting CO2 accumulate in the column. That is generally such a bad idea, I'm not going there.

I added more accurate monitoring of ph

In this case it isn't age, it is pH that is nothing but a number. You can get accurate pH values for low conductivity water, but not easily, or cheaply. That number is more precise, but I'm going to doubt whether it is more accurate. I'm not knocking pH measurement, pH is really important biologically, but it is just that pH values always need some interpretation.

Honestly the way forward is low conductivity water with some added acid (H+ ions, protons), for me it is via botanicals and, even if I added an acid to lower the pH, I would still want some humic compounds.

cheers Darrel

 

[anewbie]

Hi all,

I agree with @MacZ , probably lower, but if it is a planted tank? Then the plants will remove net CO2 from the water during photosynthesis and the pH will rise.

Plants (and photosynthesis) are a good thing for tank health, and you haven't actually increased the alkalinity level, you've just mimicked an atmosphere poorer in CO2. If you can lower the pH (with acids, fulvic and humic for me) so that it remains below pH 7 during photosynthesis? You are in a good place for black water fish.

The same applies outside of the photoperiod, you can drastically reduce pH by letting CO2 accumulate in the column. That is generally such a bad idea, I'm not going there.

In this case it isn't age, it is pH that is nothing but a number. You can get accurate pH values for low conductivity water, but not easily, or cheaply. That number is more precise, but I'm going to doubt whether it is more accurate. I'm not knocking pH measurement, pH is really important biologically, but it is just that pH values always need some interpretation.

Honestly the way forward is low conductivity water with some added acid (H+ ions, protons), for me it is via botanicals and, even if I added an acid to lower the pH, I would still want some humic compounds.

cheers Darrel

There are a few anubia and java fern in the water and quite a bit of floaters; my concern was diseases as mentioned in the thread. The tds is remaining around 26 - i can't make the tds much lower than 26 (the pen i have has two different scales (or modes to measure - 700 and 500 and i'm not sure which is more accurate for this) but the EC is 8. But (repeating my self) someone said that low tds wasn't enough that diseases will be an issue with higher ph and so i was asking what ph is required to prevent these diseases. Mac's answer was below 6 - so it sounds like higher tds (due to adding acid) is ok to get the ph below 6 and once below 6 i'm good to go.

 

[dw1305]

Hi all,

The tds is remaining around 26 - i can't make the tds much lower than 26 (the pen i have has two different scales (or modes to measure - 700 and 500 and i'm not sure which is more accurate for this) but the EC is 8.

Something isn't quite right there, the "EC" electrical conductivity value (microS / cm) should be higher than the ppm TDS value.

But (repeating my self) someone said that low tds wasn't enough that diseases will be an issue with higher ph and so i was asking what ph is required to prevent these diseases.

I know what they mean, but it isn't as simple as that, have a look at <"All the leaves are brown"> & <"https://www.aqualog.de/en/blog-en/medicinal-trees-the-common-alder/">

A simple (but good) measure of whether your tank is suitable is how quickly the leaf litter decays, it gives you a visual indication of the microbial community.

These <"inferential methods"> may not seem as scientific as chemical testing, but they are actually techniques scientists use. <"https://www.sciencedirect.com/science/article/abs/pii/S0043135419310693">.

cheers Darrel

 

[anewbie]

Hi all,

Something isn't quite right there, the "EC" electrical conductivity value (microS / cm) should be higher than the ppm TDS value.

I know what they mean, but it isn't as simple as that, have a look at <"All the leaves are brown"> & <"https://www.aqualog.de/en/blog-en/medicinal-trees-the-common-alder/">

A simple (but good) measure of whether your tank is suitable is how quickly the leaf litter decays, it gives you a visual indication of the microbial community.

These <"inferential methods"> may not seem as scientific as chemical testing, but they are actually techniques scientists use. <"https://www.sciencedirect.com/science/article/abs/pii/S0043135419310693">.

cheers Darrel

Well I'm not sure what the 700 and 500 scale are or present; the instruction manual didn't really say - it just said different applications use different scales - it is an aspera ph pen if that helps - i put in about 30 or so Catappa leaves about 6 weeks ago; the 5 hatchet fishes i put in about 8 days ago - at least 3 are still alive - all 5 might be alive but the soup is so dark you can't see much in there - when i feed them a few will come to the surface to eat so that;s how i know at least 3 are alive. As for the decay rate - doesnt' seem very fast but fast is relative - can't say much more; oh as the leaves do decay the tds seems to be rising.

 

[Ben Rhau]

The 500 and 700 scales express EC in mS/cm, not μS/cm. So, ppm500 = EC * 500, which is still not what you’re reporting.

I would verify what units your EC is and then calculate the TDS yourself. If EC is reported in μS/cm (most common) then multiply by 0.64.

 

[MacZ]

Mac's answer was below 6 - so it sounds like higher tds (due to adding acid) is ok to get the ph below 6 and once below 6 i'm good to go.

You got me wrong there. If you give it time it will drop below 6 without adding anything but humic substances. Keep the TDS/EC low, add extract of alder cones, leaves and whatnot regularly and just wait it out. Lowering pH quickly via stronger acids is not what I endorse here.

 

[martin_c]

I have just one point of critique, but that's due to my mindset ("least effort to maximum effect"): I don't get the amount of work and steps.
What I especially don't get is using mineral salts when the goal is minimum conductivity. Yes I get the point of making sure all of the singular elements are replenished, but as Ben mentioned correctly: The fish are basically used to completely deionized waters. All that extra work and extra steps seem so redundant and a bit wasteful.

A well seasoned tank based on low conductivity water can go with minimum effort.
My tank is a bit of a special example:
Base water is RO with a conductivity of 10microS/cm, I only add humic substances and botanicals. For a while I added minimum amounts of liquid ferts but that has faded out by now. On top I have about 15 meters of Epipremnum and several thickets of Hydrocotyle for plant filtration plus floaters. And as there is a lot of evaporation I refill 2-3 liters a day with pure RO. I haven't done a waterchange in months. But this only works due to the plants and the water I use. TDS are at a constant 30, pH is constant between 5 and 5.5.
Would I add a DI stage to my RO unit I could push it down to your values. so... yeah... I understand your approach, just can't understand the effort.

I'm in the same boat, i've also got Epipremnum across an entire wall, with dedicated lighting installed, and thereby no measurable nitrate/phosphate in the tank. I always wonder why i actually should do water changes at all, i guess i just want to be a good boy

My point was:
when doing water changes for black water tanks (in settings where it's necessary) we spent effort to remove (for most tap waters) at least 250µs of salts, instead of re-using the water where we only need to exchange ~25µs of salts.
In smaller tanks it's not a problem, but with really large tanks it's almost impossible, because you either need a very large storage for your osmosis water and/or need to recharge/rebuy your DI's resins a lot. I guess that's also the reason why for large black water fish species people all of a sudden propagate the opinion that those dont need black water.

Afaik the reasons for doing water changes in general are:
- resetting salts (getting rid of accumulations like nitrate, bring back what might have been consumed)
- get rid of pathogenes
- get rid of anything else we don't really know

The last point is what's probably the weak point in the method i've described. I try to tackle it with adding some activated carbon to the DI's resin.

 

[anewbie]

You got me wrong there. If you give it time it will drop below 6 without adding anything but humic substances. Keep the TDS/EC low, add extract of alder cones, leaves and whatnot regularly and just wait it out. Lowering pH quickly via stronger acids is not what I endorse here.

I think the ec is 70-80; only thing that makes sense with a tds 26; please stop saying keep the tds low - the problem is 'low' is relative. 50 is lower than 100 and 100 is lower than 200 and ....
-
I would suggest a range - between 0 and some upper limit - no clue if my current tds is over that limit - it does seem like my tds is slightly drifitng higher - maybe because of decaying leaves ?

 

[anewbie]

The 500 and 700 scales express EC in mS/cm, not μS/cm. So, ppm500 = EC * 500, which is still not what you’re reporting.

I would verify what units your EC is and then calculate the TDS yourself. If EC is reported in μS/cm (most common) then multiply by 0.64.

The pens are confusing me because they never really state the unit. All i can say is the tds is around 27 and ec is in some unit is around 0.07; my guess is that is 7ms or 70us ? would that align well with tds around 27 ?

 

[Ben Rhau]

The pens are confusing me because they never really state the unit. All i can say is the tds is around 27 and ec is in some unit is around 0.07; my guess is that is 7ms or 70us ? would that align well with tds around 27 ?

It doesn't make sense to me. Since the pens are measuring EC (and not TDS directly) you should be able to derive the ppm TDS from the EC, full stop. 27/500 - 0.054. Is it close to 0.07? Yeah, but since it's a calculation and not a measurement, I'd want to know why the two values don't jibe.

You say the pen doesn't state the unit. OK, is there any online resource, or can you ask the company that made it?

If you care about precision and knowing whether the TDS is 25, 50, or 70, you should sweat the details, IMO. I'm all for inexpensive pens as long as you know what the output means. i.e., if it's inaccurate, do you know how, or by how much? Here's what I'd do personally (obviously up to you):

1. Purchase a standard solution. 1413 uS/cm is the most common one. I usually verify against that and a lower one (23 uS/cm). Is that second measurement overkill? Maybe, but since I need to measure EC in the single digits, I want to be confident that it can measure precisely in that regime. And/or:
2. Spend slightly more money and get a more precise meter. You can get an HM or Hanna meter for about $60.

If you want to use the cheap pens, I recommend doing #1.

In either case, you don't need to rely on the pen's TDS measurement if you know what the EC units are.

You don't have to do any of this, but if not, it's hard to say whether the TDS is "over the limit."

it does seem like my tds is slightly drifitng higher - maybe because of decaying leaves ?

Possibly, or something else in tank. It's also likely a noisy number.

-B