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Featured Carbon source for macroalgae photosynthesis?

Discussion in 'Chemistry' started by GlassWalker, Apr 13, 2015.

  1. Eyore

    Eyore Guest

    No worries, you kind of answered the question already as to what is in nacl free

    Assuming you can, i would be interested to know the levels you test for ca mg kh i on your "salt mix"
    There will be some conflict and preciptation, i cannot see calcium being correct for one, but you should be able to manually compensate with balling chemicals. Sulphate loss is also a given, but this would take some thinking around this problem (i believe i will be able to tell from tested levels how much is likely precipitated)

    Post your figures for nacl and tmpm when you worked them out, i dont know them off the top of my head, but i do know how to quickly work out

    But i am sure you are already on with this and will have them already, half the fun is in the calculating lol
     
  2. Eyore

    Eyore Guest

    No worries, you kind of answered the question already as to what is in nacl free

    Assuming you can, i would be interested to know the levels you test for ca mg kh i on your "salt mix"
    There will be some conflict and preciptation, i cannot see calcium being correct for one, but you should be able to manually compensate with balling chemicals. Sulphate loss is also a given, but this would take some thinking around this problem (i believe i will be able to tell from tested levels how much is likely precipitated)

    Post your figures for nacl and tmpm when you worked them out, i dont know them off the top of my head, but i do know how to quickly work out

    But i am sure you are already on with this and will have them already, half the fun is in the calculating lol
     
  3. Eyore

    Eyore Guest

    No worries, you kind of answered the question already as to what is in nacl free

    Assuming you can, i would be interested to know the levels you test for ca mg kh i on your "salt mix"
    There will be some conflict and preciptation, i cannot see calcium being correct for one, but you should be able to manually compensate with balling chemicals. Sulphate loss is also a given, but this would take some thinking around this problem (i believe i will be able to tell from tested levels how much is likely precipitated)

    Post your figures for nacl and tmpm when you worked them out, i dont know them off the top of my head, but i do know how to quickly work out

    But i am sure you are already on with this and will have them already, half the fun is in the calculating lol
     
  4. GlassWalker

    GlassWalker Registered

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    Still working it out, as I got delayed by confusion with converting dKH to equivalent HCO3. My numbers didn't agree with UR's dosing calculator which I used as a double check. We differ on NaHCO3 although we agree for Na2CO3, so I'm still not sure what's happening there.

    Finally starting to work out balling classic, and see what you were hinting at on the other site discussions. Never realised before there were two mols of 'bicarb to one of Calcium in dosed solutions, although it is obvious now I see it, and all those sodium ions floating around need to go somewhere...

    I will have to do other things before I finish this, perhaps in the evening.
     
  5. Eyore

    Eyore Guest

    Ehsan said to me- i remind him of himself
    I have to say the same, you have a curiosity and a will to suss out what people wont reveal to you- its admirable, assuming anything i do is in fact admirable! Lol

    To answer above- i do not know why the disparity, i came across it myself 18 months back but got sidetracked onto other things and forgot to look at. I assume its in how things are expressed
    Have you sussed out the discrepancy yet?

    The amounts of sodium and chloride are known, likewise calcium, we also know the ratio of calcium carbonate.
    So using all the above you should be able to work out bicarbonate.

    I would do this, but tbh i am mega busy
     
  6. GlassWalker

    GlassWalker Registered

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    You're not the only busy person... I've decided to put all the complicated stuff to one side and go back to the core of what I want to test. As such, a moment ago I took some chaeto which was about 41.6g shaken of excess moisture, or loosely filling a 1L jug (no compression). This was put into a container in a south facing window which has 75% heat reflecting film on it, and filled with approximately 2L of 34ppt tank water and 200ml of dehlorinated tap water - volumes are not exact. Why the tap you ask? Well, the container is next to my kitchen tap and I was too lazy to walk back to the tank for a 3rd jug full! I'm in a hard water area, so there will be some extra alk, as well as free nitrates and phosphates to give the algae something to chew onto. I haven't tested my tap recently, but based in historic results it is about 10 dKH, nitrates close to the legal limit, and a generous dash of phosphate also.

    I'm letting it settle a bit now before taking starting water parameters. At a minimum I'll need to measure ppt and KH, and if I feel like it maybe Ca, nitrates and phosphates also. I don't think the rest will be relevant.

    Then the waiting begins. Note I'm not doing my control test either as I can't find my spare containers.

    On the UR calculator discrepancy, I did open a thread but as usual had no response.
     
  7. GlassWalker

    GlassWalker Registered

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    Some initial results. I set up the test container on Saturday evening, and measured the salinity to be 30.8ppt. Only the next morning did I measure the alk, and got 8.0 dKH. This evening I tested it and got 32.9ppt and 6.5 dKH. So even without taking into consideration evaporation, that's some KH drop. Out of interest, I also measured nitrate and phosphate. With the Red Sea Phosphate Pro test, the reading is 0.02 or 0.00. With the Red Sea Nitrate (non-Pro) I get a zero.

    I'm debating how to proceed with this test. I think it would be interesting to do the test with more parameters measured start and finish, and perhaps do it daily. With two points I have so far, I have an unknown error margin. With more regular testing at least I'd have some confidence by looking at longer term trends. While I don't know the starting concentration of nitrate and phosphate, there doesn't seem to be any in there now so that may stunt further growth.

    Right now I'm tempted to reset the experiment. I'd start again, and make the wider measurement of nitrate, phosphate, KH, Ca, salinity. I hope to see KH dropping, but not Ca. Salinity will be used to normalise the results as I will be unlikely to keep it exactly constant. I will aim to measure KH + salinity daily, and the others less frequently. Water taken out for tests wont be too critical with the salinity measurement, and any RO top ups wont affect the balance.

    Additional: just tried to measure the algae mass, got 43.1g but can't guarantee I shook as much water off as for the initial measurement previously. With that caution, there's a potential increase of 1.5g.
     
    Last edited: Apr 29, 2015
  8. GlassWalker

    GlassWalker Registered

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    It was all going wrong last night. I must have totally miscalculated somewhere and ended up with >30 dKH, with nitrates ~80ppm and phosphates >10ppm. I decided to dilute down with 80% fresh salt mix. I didn't have time to measure then. Tonight I remeasured and got 16 dKH which is more reasonable (H2O pro salt used has elevated KH anyway), Ca 425, nitrate 0 (checked with two different tests) and phosphate ~5ppm. Not sure where the nitrate went, as 20% of 80 should still be easily detected, unless it algae was able to consume that in one day? I just dosed ~0.14 to 0.16g of sodium nitrate into the >2L test container. Will leave it to mix a bit before I do a new measurement, but I hope it will be in the ball park of 50ppm afterwards.
     
  9. GlassWalker

    GlassWalker Registered

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    Since the reset the results are now opposite to previous. I'm seeing an increase of 0.5 dKH a day after allowing for changing salinity. Is there any mechanism for that? The chaeto seems to be in a smaller ball now. The nitrate doesn't seem to be working as expected either. After the previous dose I only measured about 10ppm, which dropped about 5ppm each day after. I just redosed and will see what happens from here.

    Pure speculation: the previous setup used tank water. Could there be enough phyto in the water to make an impact? Since I changed ~80% of the water, what's left might not have the same impact. Still doesn't explain the dKH increase though.
     
  10. GlassWalker

    GlassWalker Registered

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    This is really confusing me now... since the reset, that's 4 days of increasing salinity from evaporation, I can deal with that. Other than a dose of sodium nitrate yesterday (0.15g) I've added nothing. Measured alk tonight and the dKH, even normalised for increasing salinity, is still going up.

    Day 1: 16.1 dKH 32.3ppt
    Day 2: 16.6 dKH 32.6ppt
    Day 3: 17.3 dKH 33.0ppt, dose 0.15g NaNO3
    Day 4: 19.0 dKH 33.6ppt

    Ok, tonight's alk is even higher than expected based on previous days...

    Is there any mechanism for alk increasing without adding anything? In a previous tank, I've had some odd situations where dosing alk didn't increase the reading, but it took longer to drop after that. I was speculating if it could be converted to a form which couldn't be measured by the test kit, yet still able to be released when needed? A long stretch perhaps...

    In looking up alkalinity, one source says some organic compounds could contribute to it, but I wouldn't know were to start with that...
     
  11. rabbut

    rabbut Registered

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    I'm sure you're aware that you aren't measuring Carbonic salts directly with an Alkalinity test kit. You're measuring how much acid is needed to drop the pH to a known value and then deducing the amount of Carbonic salts in the water from the required amount of acid you used. You could easily have factors other than Carbonic salts putting either upwards or downwards pressure on pH and hence the Alkalinity reading throwing off the deductions being made regarding the amount of Carbonic salts in the water. What are you doing to control for things like fluctuating atmospheric CO2 levels, build-ups of acidic compounds and/or acidic compounds being driven off allowing the pH to require more pushing to drop to that known pH and hence skewing your readings during the test?
     
  12. GlassWalker

    GlassWalker Registered

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    I'm aware the "alkalinity" tests are kinda an everything test. I take no particular precaution against other factors, since in most cases I don't have significant control over them anyway. About the limit of my controls is taking the measurement in the evenings only, so it will be a similar point in the light cycle and thus in-water CO2 levels should be similar.
     
  13. GlassWalker

    GlassWalker Registered

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    I've been otherwise distracted recently so not done recent measurements. While in the kitchen earlier, it was quite an interesting sight to watch the algae grow even with indirect sunlight. It was giving off lots of bubbles, that the container looked like a carbonated drink.
     
  14. GlassWalker

    GlassWalker Registered

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    algaeexp2.jpg

    Right, I've decided to plot the readings I have so far. I've normalised the KH and Ca readings for a constant 35ppt. The blue line is the measured dKH, and the orange line is Calcium. Note the dots are the actual reading points. I really wish I had more Ca readings...

    Over the 16 days we see the KH was flat for about the first 9 days. Then it started dropping strongly. Calcium has dropped from a start equivalent of 460 to today's 380. This is no minor drop.

    The question arises, is the Ca drop balanced with KH? If I'm not mistaken, this is 7ppm Ca per 1 dKH. I've worked backwards from the latest reading, to see what the Ca would have been if it changed in a balanced way wit dKH. This is the grey line. It looks like to me, the start and end points are consistent with measurements (allowing for some measuring error).

    So what do we have? Nothing happening for 9 days then a steep drop in dKH, with what could be a balanced calcium consumption along the way. This doesn't prove my original hypothesis at all, which would have required calcium to be largely consistent. Something is using up that calcium, in what is essential old tank water and a bit of chaeto.

    Now, I can't say this effect is only due to the chaeto. Could there be other mechanisms in play? Very possibly. I suspect for example phytoplankton may be growing in numbers in the solution since it is far from clear now. That may be dominating the results.

    I have one more task to do some time, which is to attempt to measure the mass of the chaeto, but this was always going to be high in error due to the retained water.

    Edit: measured mass of chaeto now, got 53.6g compared to 43.1g at start. And I shook well to minimise liquid retention, and there were still numerous small frags of algae I didn't pick up as they were too small. It would seem to have certainly grew!
     
    Last edited: May 16, 2015
  15. Eyore

    Eyore Guest

    Keep the updates coming

    I really need to sit down when i have a lot of spare time to pontificate

    Biology is much lower than chemistry and maths for me

    My immediate thought (having only skim read as you update) is precipitation of caco3



    So i will ask re salinity and ph numbers and consistency?
     
  16. Eyore

    Eyore Guest

    And i only notice rabbuts post now.

    Fair point
     
  17. GlassWalker

    GlassWalker Registered

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    Salinity was somewhat uncontrolled, and I topped up manually occasionally. This started at 32.3 ppt, 33.6 at day 3, 35.7 at day 9, where I topped up a little RO after measurements. That was down to 33.7 on day 13, and up to 34.5 on day 16. I did not measure pH at all.

    I also have ORP readings but I'm not sure this adds anything, and was only done since I had an otherwise unused unit lying around. That went from 198 to 215 at day 9, then staying down to 202-ish after the RO top up.
     
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