Phosphate buffer.

Discussion in 'Aquarium Fert Dosing' started by chris1004, 3 Jan 2010.

  1. chris1004

    chris1004 Member

    Messages:
    565
    Hi,

    Is the phosphate in a phosphate buffer available to plants? In this case the buffer is waterlifes 6.5 buffer:-

    http://www.waterlife.co.uk/waterlife/65buffer.htm

    The tank in question (160litres) is going to have floating plants only, 'salvinia' and maybe some 'frogbit' to aid breeding anabantoids and no co2 injection, lighting is less than 1wpg. I'm thinking a small amount of N and K plus traces will be enough, it would be nice to get this confirmed (or not) though.

    Regards, Chris.
     
  2. dw1305

    dw1305 Expert

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    nr Bath
    Hi all,
    Chris the P in the buffer will become available, buffers work by having different solubility across a pH range. In this case the buffer will sodium monohydrogen phosphate (Na2HPO4) and sodium dihydrogen phosphate (NaH2PO4), giving you the weak acid NaH2PO4, and weak base Na2HPO4, by changing the proportion of these you can change the pH buffer range. I wouldn't ever use pH buffers (other than alkaline ones for rift Lake Cichlids etc. ), particularly if I was trying to breed soft water fish, as they will greatly increase the conductivity, (and in this case the sodium ion concentration).

    I've bred Trichopsis pumila in a similar set up, rainwater filtered through sphagnum peat, lots of moss, alder cones and oak leaves and a dense floating cover of Pistia (Nile Cabbage). If you want to breed Lace Gouramis or Siamese fighters the pH, hardness and conductivity are not important and you can use your tap water, but this set up works well for some of the more difficult ones (Chocolate Gouramis, some of the more unusual Bettas). The tricky stage is usually post hatching when the fry are very small, and need access to warm 100% humid air at the water surface (they tend to drown if not kept in very shallow water). Pistia is a better floater than Limnobium or Salvinia for this, because the leaf rosettes create humid air spaces under the rosette, in a way the flatter leaves of the other "floaters" doesn't.

    cheers Darrel
     
  3. aaronnorth

    aaronnorth Member

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    Location:
    worksop, nottinghamshire
    Too much sodium is bad for plants, so make sure you don't over-do it with the buffer.
     
  4. chris1004

    chris1004 Member

    Messages:
    565
    Hi,

    Very interesting input thanks. I do agree with your sentiments on breeding siameese fighters and pearl/lace gourami's entirely as I've bred both these fish many times, in fact pearl gourami's are very high on my all time favourite fish list and I've never been without some in at least one tank or other.

    The main reason why I'm looking at the afformentioned product is as a quick fix to create soft acidic water which also provides Po4 for plants. Now I can easily supply 100% remineralised RO water to the tank in question and because I can produce it with little or no carbonate hardness present the ammount of this phosphate buffer that I need is minimal. In fact on a 160litre tank that I have started to try this on its only half a teaspoon. Surely that can't be adding a lot of sodium?

    I don't understand conductivity at all, how is it measured? I do have a TDS meter is it the same thing?

    Regards, Chris.
     
  5. chris1004

    chris1004 Member

    Messages:
    565
    Hi,

    As a practical solution for raising fry of anabantoids what I do is to use a food grade tupperware box (the ones you get with a chineese meal are ideal once clean) with a few air holes pierced into the lid. This is then floated on the surface of the breeding tank (which has tight fitting glass covers) and filled nearly to the top with water from the same tank and lots of java moss and restrained from moving around the tank. I just change all the water periodically directly from the breeding tank through those first few weeks. I feed very fine powdered dry food sparingly 4 times a day by dabbing a wet cocktail stick into the pot of dry powder and then into the container which has a slightly larger hole to accomodate the end of the cocktail stick for feeding. It has worked well for me over the years.

    Regards, Chris.
     
  6. dw1305

    dw1305 Expert

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    Location:
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    Hi all,
    I don't see any problem in that case, although I'd still favour a weak acid (like carbonic from CO2 or humic from oak leaves etc.) and potassium phosphate as a slightly better option.

    Yes, within reason both TDS and conductivity are different facets of the same thing. It is possible to have water with a low conductivity and highish TDS, if you have "black water" with lots of organic acids etc. that add to the TDS, but don't conduct electricity. I think most hobbyist "TDS" meters actually measure conductivity anyway. Conductivity is measured by passing a small electrical current between 2 electrodes, pure H2O is an insulator, but as it becomes a solution of dissolved salts it conducts proportionally more electricity, and the reading rises.

    Assuming that all the TDS is provided by Na+ Ca"+ ions etc. the TDS / 0.64 = the conductivity in microsiemens or conductivity in microS x 0.64 = the TDS.

    Chris wrote:
    Sounds good, I've used a very similar technique for both Gouramis and Killis.

    cheers Darrel
     
  7. chris1004

    chris1004 Member

    Messages:
    565
    Hi,

    The tank isn't co2 enriched but I've got some almond leaves that I'll be putting in there I take it these do the same thing? Would you advise adding the pottasium phosphate soley as a means of feeding the plants P in addition to the buffer or instead of?


    To be honest I bought the TDS meter as a means only to check the product water from my RO unit so that I know when to change the DI resin. I don't pretend to understand it or its relationship to conductivity or what they mean in relation to a fishtank situation. I did however have a little play around with it a while back and Ed and I had some communication on the subject in this thread:-

    http://ukaps.org/forum/viewtopic.php?f=51&t=4616




    I measured the tank in questions TDS this morning and the meter reads 110ppm. I think this will fall slightly after a few water changes because there was quite a bit of the NPK mix that I use in my planted tank in there before the last water change. I'll now mix up a much leaner mix specifically for this tank but without added P.

    What sort of TDS / conductivity levels do you think I should be aiming for?


    Regards, Chris.
     
  8. dw1305

    dw1305 Expert

    Messages:
    8,267
    Location:
    nr Bath
    Hi all,
    It depends really, Rift Valley Cichlids are happy in very highly buffered "salty" water, with TDS values in the high hundreds, my tap water is very similar to Lake Malawi, and comes out of the tap relatively poor in all salts other than calcium carbonate, but this gives values of about 500 TDS. Conductivity/TDS is just a measure of the salts dissolved, it doesn't tell you what they are.

    I try and keep the TDS value below about 100, because I'm trying to keep fish naturally from water very low in dissolved salts, the value varies in the tanks between 50 and 120 dependent upon the amount of dissolved salts (probably nearly all Ca2+ ions) in my rainwater. Because my conductivity and hardness (measure of the 2+ ions carbonate ion) are closely correlated, I use conductivity as a measure of carbonate buffering. I can adjust the pH down to 6'ish using alder cones peat etc., and Indian Almond leaves would have the same effect for you.With very little buffering pH becomes more unstable, but I've never found that this bothered the fish, although it was a bit of a shock the first time I measured the pH in the morning before lights on (just over pH7 in the evening, but just under pH6 (10 times more "acid")in the morning. At pH6 I can keep "black water" fish successfully, but for Dicrossus filamentosus for example the fish spawned but never managed to successfully hatch any eggs, people who have been successful with these have used very extreme water values with no detectable hardness and pH values down to pH4.5 (although with no buffering this may actually be a very small amount of acid present).

    Other posters on this forum will tell you that the conductivity is irrelevant to fish, with the added nutrients giving values of over 700microS (over 500TDS).

    cheers Darrel
     
  9. chris1004

    chris1004 Member

    Messages:
    565
    Yeah I've noticed this too and that may be on top of using tapwater with high TDS in the first place, I know my tapwater is usually about 380ppm living just outside London (Dunstable), but because of the Chiltern hills around us our water is very very chalky.

    However we all have our own views and sometimes fish will breed in seemingly adverse conditions further clouding water quality issues, we've all heard "I bred discus/rams etc. in tapwater" reports, which I don't doubt happens sometimes. I'm pretty sure there's more to it than just getting the water right, certainly happy healthy fish is as if not more important.

    Regards, Chris.
     

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