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Help me pick a ph. (co2 injected tank)

Discussion in 'Apistogramma' started by sherry, Jan 31, 2006.

  1. sherry

    sherry New Member 5 Year Member

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    I have just begun injecting co2 into my planted tank. As a result, I have exact control over the ph of my water.

    My kh/gh are both 2.

    I am trying to do this without additional buffering if I can.

    Oh and running my controller without the co2 plugged in told me that my co2 is 6.5 in the morning (after the plants have been on lights out all night) and 6.7 in the evening. The plants make o2 during the day, but at night become a drain on the air supply and make a lot of co2 ... so at night, I run a bubble stone to keep the fish happy and safe.

    I calculate that by running the controller at 6.4 I am adding 12 ppm of co2 for a total of 16 ppm.. the tank and fish can handle a twice that easilly since co2 does NOT replace o2... but I want to make sure I'm not making the water too acid.

    So, in a tank with Apisto cacs, soon to be evicted rummynose tetras, soon to be added pencil fish, otos, a couple of bristlenose plecos and some featherfin rainbows, how low a ph can I maintain?

    I'd love to get the co2 concnetrations at 6.3 or 6.2 if that is okay for the fish. The charts say 6.3 gives me a perfect 30 ppm of co2, but since my starting "natural level" shows up on the chart as 12 and since that is probably 8 points off -- tanins may be driving the ph down further -- I am assuming that starting 12 is really a 4 so I subtract 8 ppm from the total.. which makes the ideal co2 levels possible at ph 6.2.

    I can buffer and bring the co2 concentrations UP without lowering ph any further, but given the controller as a safety net and the fact that the co2 doesn't look like it is bouncing around at all, it seems reasonably safe to let the kh2 stand (tho I can be talked out of this if I am making assumptions that don't hold up)

    thanks!!!
  2. Chris(wildcaught!)

    Chris(wildcaught!) New Member 5 Year Member

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    Hi sherry!

    If you can keep the pH value stable at 6.2 or 6.3 it should be alright for the fish.

    But.. I have no clue what a featherfin rainbow is for a fish. So I can't say anything about pH for that species.

    Regards / Chris



  3. sherry

    sherry New Member 5 Year Member

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    right now all of my fish do okay in acidic water..

    I did decide to buffer a tiny bit tho.. because someone I trust pointed out that my kh2 may actually be a little lower which could lead to ph swings.

    I am trying to use just about a tablespoon of crushed coral in the filter to bring kh up to 3. That is said to be a very stable point.

    then I will probably keep the ph at around 6.2/6.3.

    :) thanks!!!
  4. aspen

    aspen Active Member 5 Year Member

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    you are monitoring ph with a controller adding co2, and also gradually adding kh with crushed coral. what is preventing the coral from dissolving and raising kh, then the controller adding more co2 to combat this? won't you eventually end up with a co2 over dose? you cannot really tell what the actual co2 level in ppm is once you have an unknown level of alkalinity from the crushed coral. so how would you be able to calculate co2 levels?

    if i wanted to raise the kh, i'd do it with a measured dose before trying to lower with co2. then you have a fixed place to work from to lower the ph.

    rick
  5. David W

    David W Guest

    I think personaly a KH of 2 is very low, it will not have a very good buffering capacity. Plants will not do well either, you need a KH 3 to 4 GH 6 to 8.
    If you can Dennerle do a book Its about their system it gives a lot of help in the suject you are wanting information on £13.00

    :)
  6. sherry

    sherry New Member 5 Year Member

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    I have used a tablespoon of cc to raise the kh to 3... Aspen you do add MORE co2 to now work with the new kh level, but you also keep track of the kh, meaning if the tablespoon brings the kh higher than 3, you start to lower the amount of cc in the filter (micron bag). It is a little bit of a balancing act, but once you get a stable kh, it remains so.. or so I am told.

    It takes a lot of co2 to make an overdose, and with a kh of 3, and a ph set at the moment of 6.4, I am pretty far from those levels. Indeed I am lower than most planted tank folks would recommend.. but I want to be gentle with it.

    kh of 2, for those of you who gently scolded .. was too low.. I was risking ph swings even with the controller. NOT good for the fish.

    so far everyone seems to be doing well, but I am monitoring closely.
  7. aspen

    aspen Active Member 5 Year Member

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    sherry, a co level of 30 ppm is considered the highest you'd want.

    what kind of filter are you running?

    i have seen shrimps pass out before the fish are hurting, this is a reason people like to have them in their tanks. that is, the white ghost shrimp ime.

    i personaly don't think that your kh was too low, these are softwater low ph fish. but you are being cautious for now. watch and see, most of your plants will go nuts. but they should at least be pearling nicely when things get going.

    there is nothing wrong with cheking the ph of your tank carefully, and drawing a sample and aerating, then checking this again. i believe it is more accurate to 'back check' your real tank parms esp after you've been adding stuff and changing water. with some exp you'll see pretty close what the co2 levels are, by watching fish behaviour and plant growth in the day.

    good luck, rick
  8. Cumb Dunt

    Cumb Dunt New Member 5 Year Member

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    a great way to find out how much CO2 you are REALLY adding is to find out how much of your pH is actually composed of carbonic acid.

    take an ounce or two of your tank water and let it degas (that's de-gas) for 24 hours. then measure the pH of your sample.

    to get enough CO2 for plants, you are looking for a pH drop from your measurement of about 1.0 pH units. so if your degassed water is 7.1, then i would set your controller to 6.1 and leave it there.

    the reasoning behind this is that your pH test kit really measures the acid content of your water, but not all of the acids present will be the result of CO2. if you are running peat, you will read the tannins as well, as long with other organic acids.

    if you want to keep your water soft but add KH, try adding a small quantity of dolomite to your filter bags.
  9. Cumb Dunt

    Cumb Dunt New Member 5 Year Member

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    i can say safely that i have had fish show no signs of stress in CO2 levels up to 90 ppm.
  10. sherry

    sherry New Member 5 Year Member

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    Where do you find dolomite? I have called the garden center stores, searched on line... I know it is the same thing as crushed limestone, but I can't for the life of me find any!!!!

    I also know it is slightly preferable to crushed coral in that it has a better ration of calcium to magnesium in the gh portion.

    do you have some? can i buy a cup? I am using a tablespoon at a time of coral.. a cupper of dolomite would take me a long way!
  11. Cumb Dunt

    Cumb Dunt New Member 5 Year Member

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    i don't have any, no.

    it was the big thing a few years ago in saltwater systems, or so i hear.

    i can't find it anywhere either.
  12. Christine-FishGrrl

    Christine-FishGrrl New Member 5 Year Member

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    The EASIEST way to raise KH (not GH) is simply to add 1/2 teaspoon of Baking Soda to the tank. You do want a KH higher than 2 because the CO2 will eat away at the buffer. KH of 3 or 4 is much safer. Check out Rex Grigg's Guide to Planted Tanks www.rexgrigg.com - there's a lot of awesome information whether you're a beginner or been doing it for awhile. There's also a detailed KH/pH/CO2 chart on the site.

    I've been keeping my pH in my tank with Apisto. trifasciata about 6.4 - 6.6 for a long time now with no problems. The CO2 stays around 30 - 50 ppm which is not a problem as long as you have surface movement at night.
  13. sherry

    sherry New Member 5 Year Member

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    yes. the reason, btw that you want surface agitation at night isn't that your co2 goes too high (especially not if you ahve a controller) but that your plants become HUGE consumers of oxygen and suddenly compete with the fish.

    most of us with co2 injected tanks have lots of plants and therefore need to keep the surface moving at night to keep the water oxygenated. co2 doesn't crowd out oxygen. the two can subsist at high levels together.. but oxygen does get used up