plants ?pearl following water change

Discussion in 'Aquarium Fert Dosing' started by davideyre, 27 Mar 2008.

  1. davideyre

    davideyre Member

    Messages:
    34
    Location:
    Oxford
    i have a 6 week old 125litre setup with about 1.5wpg of light and diy co2 (my drop checker with 4dkh water is consistenly green). am using james' pmdd.

    following a water change (changing between 25-50%) my plants (and unfortunately the algae too!) seems to pearl for the rest of the day in a way they don't at any other time. what is likely to be in the tap water that does this?

    is it -

    1. not pearling at all but chlorine coming out of the water as gas bubbles, i add dechlorinator to the tank and then top it up with a hose. this seems unlikely as the most light exposed plants seem to pearl the most, with the lower leaves not doing so.

    2. the tap water contains much higher co2 levels. this is hard to tell as the drop checker gets out of contact with the water and turns blue in contact with the air while the water change occurs, however once back in contact with the water it appears roughly the same green shade.

    3. there is a nutrient in the tap water that i am under-dosing. as an experiment i doubled the dosing of everything, but could not reproduce the pearling, even transciently. (testing with my imperfect test kits suggests that nitrate ~25, phosphate high at 5.0 (up from previous levels because of doubling up fertiliser), iron 0.5-1.0, potassium not tested! but sure high too!!).

    i guess my money would have to be on number, co2, but wanted to reassure myself was not gassing the fish with loads of chlorine or alterantively missing something else? any thoughts?
     
  2. Ed Seeley

    Ed Seeley Member

    Messages:
    3,262
    Location:
    Nottingham
    If you're using tap water then it is colder than your tank water when you add it. Colder liquids hold more dissolved oxygen and as this is added to the tank and warms all that oxygen (and some other gases too) cannot remain in solution. This leads to superstauration at worst that can harm fish, but usually the gasses just bubble off. As the water is nearly saturated with oxygen that produced by your plants is now unable to dissolve easily and then you see pearling.
     
  3. davideyre

    davideyre Member

    Messages:
    34
    Location:
    Oxford
    thanks. am using a mix of warm and cold water so although the water is the same overall temperature as the tank it started out as mostly cold water with more oxygen dissolved in it, makes sense, thank you very much.
     
  4. nry

    nry Member

    Messages:
    1,239
    Location:
    Cumbria, UK
    Am I wrong in saying that tap water actually has quite a high CO2 content? I recall such a discussion from a different forum ages ago.
     
  5. Ed Seeley

    Ed Seeley Member

    Messages:
    3,262
    Location:
    Nottingham
    I have heard that too, although I have heard the opposite as well! I've never seen any conclusive evidence either way.
     
  6. GreenNeedle

    GreenNeedle Member

    Messages:
    2,706
    Location:
    Lincoln UK
    This is the main reason for zero water changes in a non CO2 tank.

    Tap water holds more CO2 than the tank water in a non CO2 will have in it therefore doing a water change unstabilises the CO2 level and then.....

    This is what TB says anyway. He will probs confirm. lol

    Andy
     

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