Can I make blackwater using my tap water?

[Mazan]

As I mentioned in another thread, I want to try to breed my dwarf pike cichlids, but I am pretty sure I will need to have real blackwater conditions, as they have not showed any signs of breeding so far. But my water is already very soft. I hadn't measure the parameters for a long time but decided to do so today to check, hopefully my tests are still Ok as I have had them for quite a while. Anyway this is how my tap water (which comes from a mountain river and is not treated in any way) comes out:

GH 1
KH 0-1 (does not change colour on first drop, turns yellow on second)
pH - 6.8 (Azoo kit), 6.5 (Sera kit )(??)
TDS 21, conductivity 42

In the aquarium I will move them to, which is well established and planted, at the moment it has 16 baby Guianacaras 2-3cm as well as some Copellas, and a few other small fish, all will be moved next week.:

GH 1
KH 0 (yellow on first drop)
pH 6.6 (Azoo) 6.2-6.4 (Sera) - first thing in the morning
TDS 17

Re leaf litter - I used to have a lot in that tank, but removed it recently as I started to get an outbreak of Cyanobacteria. They were locally collected leaves that last quite long but do not seem to produce much tannins even when boiled, Catappa leaves are only sporadically available and much less often now since the best local shop has closed down. I do have a bag of alder cones - the Andean species (Alnus acuminata), they look the same but I haven't tried boiling them yet. I can buy various blackwater extracts - Azoo "triple black water", Dymax "ultra black water" and Dymax "The Black". There is already a lot of driftwood in the tank. I should be able to get peat but a bit nervous getting it from a garden centre in case it has something else added. I did try peat once before that a local fish shop owner gave me, but it had no effect on pH, maybe didn't give it enough time and I did not prepare the water for water changes. The tank measures 120 x 40 x 50 cm, but a lot of the volume is taken up with driftwood and substrate.

Any suggestions?

 

[Mazan]

Just for comparison I tested the water in the big tank where the pike cichlids are currently. It s only slightly different:

GH 2
KH 1 (1st drop blue, second yellow)
pH 6.6-6.8 (can't tell, Azoo), 6.5 Sera.
TDS 36

 

[Mike Wise]

I would think that your tap water should work since it is so soft. You'll need to get the pH <5.5 for your pikes - but remember that pH fluctuates in soft water and is not always dependable. I make blackwater in a separate tank and only add it to an aquarium with fish during water changes. I cycle water through peat but any acidifying organic should work.

 

[Mazan]

Thanks, I do have a spare tank that I could potentially use to prepare water, as long as I don't have to heat it continuously. I'll give it a go anyway, nothing to lose.

 

[Ben Rhau]

If pH is really the limiting factor, I think peat or strong acid are the only solutions. Of course, all precautions apply. I would personally avoid the blackwater extracts because they're unlikely to be acidic and will only increase your conductivity.

 

[martin_c]

@Mazan If you're going to push the PH to the lower end you might consider electronic PH measurement.

 

[Ben Rhau]

Yes, I found that necessary.

 

[Mazan]

I need to get a proper pH meter then, I had one, a cheap one but it was totally useless!

Just a quick question, if the tank has a lot of leaf litter etc. does this not help to stabilize the pH?

And if so would it work with my leaf litter that is not apparently rich in tannins?

 

[Ben Rhau]

Leaf litter will have close to no effect on pH. You can confirm this yourself by putting some in a jar with distilled water vs water only. I've done this to test a number of different organics, and the only one that lowered pH was peat or peat/sphagnum moss. Some types of driftwood also worked, but that effect is very temporary.

The pH meter is a bit of a chore. It sounds like you're scientifically inclined, so you may be aware that it requires frequent calibration and keeping the probe wet at all times.

 

[martin_c]

Maybe i'm wrong but i felt like @Mazan's question went in the direction whether leaf litter can protect the PH from collapsing.

Indeed it's said that if it's not a sterile tank but a tank with mulm / leaf litter / detritus which gives home for bacteria those bacteria somewhat keep the PH stable in the long run.
I've also made that experience when i was experimenting with different PH values for my Heckel discus a while back that after changing the PH either upwards or downwards it was slowly resuming to the former PH value.

 

[Mazan]

Leaf litter will have close to no effect on pH.

Agreed, I have learned this by experience, it doesn't make any difference, or hasn't ever in my tanks, even when I was using almond leave, which did stain the water.

Re the pH meter, I do still have it but came with only enough of the chemicals to calibrate it once, and I haven't been able to get more. Maybe I didn't try hard enough. But it lost calibration very quickly.

Maybe i'm wrong but i felt like @Mazan's question went in the direction whether leaf litter can protect the PH from collapsing.

Yes, that is what I meant.

 

[martin_c]

Re the pH meter, I do still have it but came with only enough of the chemicals to calibrate it once, and I haven't been able to get more. Maybe I didn't try hard enough. But it lost calibration very quickly.

If your cheap ph meter's display happens to have a bnc port, you could by a decent glass electrode and re use the display.

 

[Mazan]

I'll check it out, but its a very basic one...

 

[Ben Rhau]

Maybe i'm wrong but i felt like @Mazan's question went in the direction whether leaf litter can protect the PH from collapsing.

I see. In that case, let me say there is no danger of the pH collapsing. Dissolved CO2 from the air will generate KH (via the carbonate - carbonic acid equilibrium) and the pH of neutral water wants to stabilize at around pH 5.5.

I've found that even adding strong acid, I can lower the pH below that, but when I check it the next day, it wants to go back up to 5.5. You need to add enough acid to neutralize this. You'll observe this when you try it.

Finally, for the sake of argument, let's say the pH were actually to fluctuate wildly, as many fear. Theoretically, this would happen because there are so few ions that it doesn't take many to change the pH measurement. But the water itself isn't radically different plus or minus a few ions. It's just an unstable number describing a very dilute solution.

 

[dw1305]

Hi all,

Re the pH meter, I do still have it but came with only enough of the chemicals to calibrate it once, and I haven't been able to get more. Maybe I didn't try hard enough. But it lost calibration very quickly.

They need calibration every time you use them, and you really need a meter with "2 point calibration". The other problem is that pH meters aren't very good with low conductivity water, and this applies even to more expensive lab. type meters.

You can stabilise the reading with a "neutral salt" (like NaCl), this adds conductivity (via Na+ & Cl- ions), but doesn't change the pH

If you really wanted to measure pH accurately in these sorts of tanks you would need

• a <"solid state ISFET pH meter with REFET reference electrode">, and
• a lot of spare money.

Personally I'd <"go for lots of leaf litter"> and <"some citric acid">?

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">.

cheers Darrel

 

[MacZ]

Leaf litter will have close to no effect on pH.

Well, yes and no. No immediate effect at the least. It takes months and the addition of lots of leaf litter in very soft (no detectable KH) water to bring pH down that way. Once it starts rotting on a certain baseline level pH stays down. Still regular addition of humic substances is a big help. What source they come from is secondary.

 

[Mazan]

If you really wanted to measure pH accurately in these sorts of tanks you would need

• a <"solid state ISFET pH meter with REFET reference electrode">, and
• a lot of spare money.

Personally I'd <"go for lots of leaf litter"> and <"some citric acid">?

OK I certainly do not have a lot of spare money! So I guess using the Sera pH kit for now will at least let me know if the pH is starting to go down, I guess the exact value is not that important...and thanks a lot for the links, I will read through all these carefully later today. But its looking as though I should try peat again, get whatever leaves I can, only this time I will prepare water for water changes in a separate tank or container instead of just using tap water. Maybe I should try one of the blackwater extracts as a backup too?

 

[Ben Rhau]

OK I certainly do not have a lot of spare money!

A number of folks on this forum have had good luck with the Hanna 98129, which is certainly not cheap at $200, but cheaper than what Darrel is suggesting. I believe it has a glass electrode as opposed to ISFET. It has a cap where you can put a few drops of buffer to keep the electrode wet. However, the cap is not airtight, and if you leave it for more than a few days it will definitely dry out. You can get around this by storing the unit upright in a beaker with some buffer at the bottom, sealing the top of the beaker with saran wrap or parafilm, like they do with more expensive probes.

I didn't calibrate mine every time (like you should for proper research). Instead, I would test it against a standard that's close to my target pH. If it was accurate, I didn't recalibrate. Still, this is all added effort, and you do need to periodically buy the standards and cleaning solution. I quite like not having to worry about pH anymore.

Personally I'd <"go for lots of leaf litter"> and <"some citric acid">?

Citric acid would work, but I think strong acids are simpler to use because they don't degrade. You just need to be careful with them and buy the dilute ones that they often sell for hobbyists. The "pH Down" product is simply 1M sulfuric acid.

Maybe I should try one of the blackwater extracts as a backup too?

The problem with these extracts is that humic and fulvic acids aren't very soluble in water at acidic pH. If they're present in any appreciable concentration, they need to have a strong base added (often NaOH) to remain in solution. The resulting solution will be neutral to alkaline, which isn't the effect you're looking for.

 

[Mazan]

Ah OK, thanks for this information!

 

[martin_c]

I don't really see though why a glass electrode shouldn't be sufficient in very soft water.
It might take a while for a final result but if you have the electrode attached to the tank permanently (like i do) that's not an issue.
I calibrate it like every 2 months or so. If it's been a while since calibration i know that i take the result with a grain of salt, but i don't need high accuracy anyway. It's totally okay for me if it's misleading by 0.1 or even 0.2. My personal rule for black water has always been "the 4 must stand".

My current PH Display (Greisinger G1501-GL, combined with a Dupla glas electrode) has this nice feature that after calibrating it tells you in percentage how good the electrode is performing. So you know if it's time to change the electrolyte fluid or even the entire electrode.