# Other Aquarium Forums > Fish Care, Nutrition and Water Management >  Does blackwater extract bring down your pH ? REALLY?

## GaspingGurami

Hi, over the weekend, I was trying to acclimatise some new fish to my tank. The TDS of water in the bag was 800+ppm while my tank was 150ppm. Looks like a long wait is in the making this weekend, for me. So to kill time while I waited, my idle mind conjured up mischief  :Grin:  for me after I am reasonably sure the new fish won't die of ammonia poisoning as I dropped in some Seachem Prime to neutralise the N. So I got to thinking, wondering...

Blackwater extract is supposed to be rich in humic and fulvic acids. From what I understand it to be, these "acids" have a high pH. But don't ask me why it's called "acid" when it has a high pH :Confused: . The scientists call them acids, so acids it be. Anyway, I did a little experiment with what I have at hand, and I thought I'd share the results with you here.

Poured out a cup of distilled water, stir and expose to air so the pH will fall to ambient levels as atmospheric CO2 gets dissolved into the unbuffered water. pH tested with pH pen calibrated to pH 7.0 fell from 7.0 to 5.0 and held there. After it stabilised at pH 5, I checked the TDS of the water - 4µS (2ppm). Now is time to start the testing. Note: both instruments are ATC so temperature compensation is automatically factored in.

Test1:
Poured half of this distilled water into another cup. After pouring, I realised I didn't clean that cup :Embarassed: , so I test TDS and pH again to get new baseline. 14µS (7ppm), pH 5.5. Whatever residue was in the cup had buffered the water by a bit, but it is still pure enough, so with this new baseline, I proceeded to add in some Blackwater Extract. The amount added is not important, for I just wanted to know how it will react when diluted to form a stock solution. The result: TDS 102µS (51ppm), pH 6.5. 

Poured this mixture into my 1ft cube with original TDS at 150ppm, 7.0 pH. After adding in the Blackwater mixture, parameters remain unchanged.

Observation: Blackwater Extract added in some 44ppm of minerals which increased the pH to 6.5 in the stock solution, but when diluted into 23L of tank water, the tank water turned yellow, with no measurable change in TDS and pH .

Test 2:
I washed and rechecked calibration of my probes and tested the remaining distilled water from the cup. Still pH 5.0, TDS 4µS (2ppm). I added some dried ketapang leaves and left it to soak overnight. Next day, the water had turned a tea colour as expected. pH fell to 4.5, but TDS increased to 222µS (111ppm).

Observation: Ketapang leaves added acids and 109ppm of minerals to the water. I did not bother to test KH nor GH of both stock solutions as the dark coloured water will be difficult to discern the colour change.

Conclusion:
Will Ketapang or Blackwater soften your water? Frankly, I dunno, but I doubt it will remove whatever hardness that's in the water. Conversely, it'll add a bit more minerals to your water which may be good or bad, depending on how you want it to be.

In the 2 tests, I see that Ketapang acidifies the water while adding some dissolved minerals. Blackwater Extract increased the pH to 6.5 while also adding in a lesser amount of dissolved minerals. As no test was done to establish the KH and GH of the water after addition of Ketapang and Blackwater Extract, it is unknown whether any of the introduced minerals will increase hardness.

If your objective is to lower the pH of your water, then Ketapang is seen to do that, and best of all, it is free. But considering that it adds a fair amount of minerals to your water, for that bit of pH reduction, I figure you'd be better off adding in some vinegar or lemon juice to lower the pH. Or use CO2 for those who is blessed with high tech equipment - it lowers pH without increasing TDS.

OTOH, is Blackwater extract a waste of money? I dunno. There is certainly value in Humic and Fulvic acids - the organic carbon is good for health not only for plants, but also for people, as I use Humus for my Chilli and Mulberry plants to excellent effect.

Hope someone more knowledgeable will chip in and widen the knowledge.

----------

