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Hello everyone! Long time no post…I do not currently have any paroes, but I am setting up a 5 gallon/20 liter black water tank that will likely wind up housing either paroes or coccina complex wild bettas. This tank has only been set up for just over 3 weeks and will not have any fish for several more months, but it has already provided a variety of useful insights on keeping tanks that are this soft and acidic…here is one such discovery;
From the time I set the tank up, I intended for it to have a conductivity no higher than 40 microsiemens (25 ppm TDS) and a PH in the range of 4-5.5. Keeping the conductivity that low has not been challenging, but the same cannot be said of the PH…the tank’s PH has been at 6 for most of that time, and even adding API PH down (a 9.6% sulfuric acid solution) to my 40% water change at double the recommended dose (for the 2 gallons/7.56 liters I added) did not hold the PH lower than 6 for more than 12 hours. I did a variety of tests to see if carbonates were being added by accident…and found none; the substrate is leaves, peat moss, and sand (all of which tested inert when I set the tank up with distilled water), I am lightly fertilizing the tank with Thrive C (which turned out to be quite acidic when I tested it and is definitely not the culprit, though using the full dose will cause the conductivity to rise faster than desired), I am feeding the tank with a small amount of fish flakes to mature and perhaps cycle it before the fish arrive (the flakes do not contain carbonates either…I tested them with vinegar outside the tank and no reaction resulted). I even speculated about whether sulfur reducing bacteria had established themselves in the tank…but judging from the lack of a pronounced rotten egg odor (from the hydrogen sulfide they would produce in the process), they are probably not growing in sufficient quantities to be the culprit. However, I think I have figured out what is happening.
You see, when CO2 dissolves in water (inevitable in tanks with any surface agitation) some of the CO2 is converted to carbonates, with the exact proportion depending on the PH of the water it is being dissolved into. Using a CO2/carbonate calculator revealed that a tank with a PH of 6 and with a fairly normal CO2 level of 3 ppm can have about 1.8 ppm carbonates…that doesn’t sound like much, but when the molar mass of carbonates and sulfuric acid are taken into account that is more than enough carbonate to neutralize all the acid I added to the tank in the aforementioned water change. The quantity of carbonates produced falls sharply as the PH drops, so if you can overcome this initial ‘hump’ keeping the PH low will be markedly easier. Just thought this would be helpful to those who – like me – want low PH black water tanks.
Hi everyone! I finally got the PH below 6 long term…it is currently around 4.5 (I did the 40% water change yesterday). I used 1.25 ml of the aforementioned API PH down – easily enough to neutralize all the carbonates that the tank acquired from simple gas exchange. This also sent the conductivity shooting up to about 47 microsiemens/29 ppm TDS in the tank…thankfully the tank will now produce carbonates much more slowly due to its lower PH, so I will not need to add nearly as much acid (and thus conductivity/TDS) next time to keep the PH down.
Hello Joshua
Thank for telling us about your work on ph reduction.
Personally for me its a bit difficult to understand, – but its always good to have inforamtion for others to use.I want to take this opportunity to tell you that unfortunately our forum is not very active any longer, which is why theres not a lot of answers to posts made here lately.
I hope this will change in the future, – but right now I just wanted to let you know.
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