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Thread: RO and blackwater?

  1. #1

    Default RO and blackwater?

    I've finally got an RO unit (for pretty cheap too, $40) and it'll help me a lot with my projects that'll need RO water (native blackwater tanks and reef tanks). What I need to know is how to get RO water into blackwater conditions, with a pH of 6.8 at most, a GH of between 2 and 4, and kH (which is the stability, right?), umm, high enough to prevent swings lol. So should I add tannins/blackwater extract to the RO water to achieve blackwater? On a side note, I'll be DIYing a tannin reactor (a reactor stuffed with leaves and other plant material) to keep the water nice and brown.

  2. #2
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    I find Ketapang(Indian Almond) leaves are good....Plenty of sourced on-line

  3. #3
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    I use Tantora Catappa Tea bags, which are crushed Indian Almond Leaf, generally the tea bag contains the leaf as they break down, less messy. I just use 1 tea bag in the tank and replace every two weeks or so. My blackwater tank also has bunch of wood which is still leaching tannis after months of soaking and being in the tank for about 4 months now.

    As for using RO and blackwater I am not sure, I know my GH and KH levels are really low in my blackwater tank and by injecting co2 my ph is just above 6.

  4. #4

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    So basically, all I need is a source of tannins? I guess I’ll go out and get some today then lol. I’ve always preferred using the local stuff, eucalyptus leaves and branches, which produce the same dark tannin tint IALs make.

    Will I need to worry about pH swings?

  5. #5
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    What's your target pH? That will determine how you go about mixing your RO and minerals.

  6. #6
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    I'm with Rebel here, depending on what your starting point is and what your target is will determine what you will do. But if your only aiming for 6.8pH, RO water mixed with tap water + some leaves, alder cones and/or similar should get you there depending on your tap water paramateters. 6.8pH is not very "blackwater" IMO. The Reactor might be a little over kill too.

    What are you aiming to keep, blackwater wise?
    "The stuff I buy is a bit pricey however it is as dry as a nuns nasty" - BigDaddyAdo

  7. #7

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    Between 6 and 6.8, not too low as to where nitrifying bacteria won’t operate, but still within a comfortable pH range for the fishes.

  8. #8
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    6.8 means that pure RO would almost get you there with a couple of indian almond leaves depending on volume of water. What's your target TDS?

  9. #9
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    What fish are you keeping? Not too many fish really need a particular pH to do well. Mostly its around egg fertilisation for wild caught fish, and a few blackwater species. You may be able to get away with just replicating the blackwater environment using tannins.

    Side Note - I have kept tanks as low as 4pH with no issue to nitrifying bacteria that I am aware of
    "The stuff I buy is a bit pricey however it is as dry as a nuns nasty" - BigDaddyAdo

  10. #10

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    6.8 is the maximum, preferably lower. As for TDS, not sure, I’m unsure about what TDS would be preferred by soft water fishes.

  11. #11
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    Usually lower the TDS the better do certain fish. Which fish are you trying to breed?

  12. #12

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    Quote Originally Posted by indir View Post
    What fish are you keeping? Not too many fish really need a particular pH to do well. Mostly its around egg fertilisation for wild caught fish, and a few blackwater species. You may be able to get away with just replicating the blackwater environment using tannins.

    Side Note - I have kept tanks as low as 4pH with no issue to nitrifying bacteria that I am aware of
    I thought bacteria didn’t like such low pH, or did you cycle the tank with an already low pH, causing low pH bacteria to grow? I want to keep galaxiella and salamanderfish, all species that originate from a soft acidic environment, and do not tolerate hard alkaline water. Plus, i intend to breed them, so Blackwater will definitely help.

  13. #13
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    Sounds like specialised fish. I would suggest getting an idea of exact TDS and pH that you want to aim at. Usually soft water has TDS of less than 100. Extreme soft would be 30.

  14. #14

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    They are definitely specialised fish haha. In that case, a TDS of 40 - 90 and a pH of 6.5 is what I’m aiming for.

  15. #15
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    Have you checked the resultant TDS from your RO water outlet? Hopefully you are getting close to 0. To remineralise, people usually use something like Seachem equilibrium to make it up to the TDS that you want.

    I reckon your pH will be close to that with the RO alone. Probably only need to add some almond leaves etc to get it to that level.

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