Determining The Water Volume Of Your Whole Reef System

Discussion in 'Water Chemistry' started by ReefSparky, Aug 12, 2008.

to remove this notice and enjoy 3reef content with less ads. 3reef membership is free.

  1. Matt Rogers

    Matt Rogers Kingfish Staff Member

    Joined:
    Dec 31, 2000
    Messages:
    13,466
    Location:
    Berkeley, CA
    No digits.. just the notches so to speak.
    I do have a lot of rock, around 2lbs per gallon if I recall correctly and a 4" sand bed.
     
  2. Click Here!

  3. blackraven1425

    blackraven1425 Giant Squid

    Joined:
    Mar 1, 2010
    Messages:
    4,780
    Ok, so I gather you're using a hydrometer for this? And I'm also guessing, about 70-75 lbs of rock?
     
  4. Matt Rogers

    Matt Rogers Kingfish Staff Member

    Joined:
    Dec 31, 2000
    Messages:
    13,466
    Location:
    Berkeley, CA
    No it is a refractometer. But not digital.
     
  5. blackraven1425

    blackraven1425 Giant Squid

    Joined:
    Mar 1, 2010
    Messages:
    4,780
    Well, here's something to consider:

    ( x * 1.0262)+(1*.5) = (1.0259 * (t + 0.5)) solves to x = 43.1, which gives a ttoal tank volume of 43.6 gallons

    ( x * 1.0263) + (1*.5) = (1.0257 * (t+ 0.5)) solves to x = 21.4, for a total volume of 21.9 gallons

    ( x * 1.0262) + (1*.5) = (1.0258 * (t+ 0.5)) solves to x = 32.25, for a total volume of 32.7 gallons

    So, the accuracy necessary to measure for this equation to be accurate is really high. Any of those numbers can fit with your description of your refractometer's reading, at least as I'm understanding it.
     
  6. Matt Rogers

    Matt Rogers Kingfish Staff Member

    Joined:
    Dec 31, 2000
    Messages:
    13,466
    Location:
    Berkeley, CA
    Yep you are right. And I am working with a low volume of water added.

    So get this...

    I just used the 3reef Advanced Water Volume calculator:
    3reef.com - Forums for coral reef aquariums, salt water fish, corals, inverts, protein skimmers, aquarium lighting and more - Calculators

    I used:

    Total Gallons of water in tank, sumps, Refugium, etc. (estimate) 50
    Cubic feet of LR and sand (Estimate) 2.0 (4" sand bed plus 60-70 lbs of rock) EDIT - I SAW ONLINE SOMEWHERE THAT 1 cubic foot is about 80 lbs. Using 3reef sand calculator - I have 109+ lbs of sand
    Current Salinity in PPT (exact) - 36.3 PPT

    How many gallons are you adding? .5

    After adding water and waiting for equlibrium what is your new Salinity? 35 PPT


    Final Information​
    Percent Change: 3.58%
    Actual Volume in Gallons including the addition of your test water: 34.28

    Something close to 30 gallons again!

    hmmm.. starting to feel better about that number now..

    matt
     
    Last edited: Sep 19, 2010
  7. blackraven1425

    blackraven1425 Giant Squid

    Joined:
    Mar 1, 2010
    Messages:
    4,780
    Isn't that just ReefSparky's equation (one you doubted before) implemented in JS?
     
  8. Click Here!

  9. Matt Rogers

    Matt Rogers Kingfish Staff Member

    Joined:
    Dec 31, 2000
    Messages:
    13,466
    Location:
    Berkeley, CA
    It's his but it has fields for sand and rock volume - etc.. not sure why that one comes up with a better number. Lets see when he chimes in. :)
     
  10. blackraven1425

    blackraven1425 Giant Squid

    Joined:
    Mar 1, 2010
    Messages:
    4,780
    I think it's because it's his original equation, not the second one. The original required estimating the current volume of the system.
     
  11. ReefSparky

    ReefSparky Super Moderator Staff Member

    Joined:
    Nov 27, 2007
    Messages:
    3,675
    Location:
    South Florida
    Hey Matt. I'm kinda swamped today, so I'll respond having not read everything you posted--but enough to think I know what the issue is. To borrow a word from the electrical discipline, when it comes to instrumentation--there are all sorts of adjectives that describe how close we are able to get in our measurement. Accuracy, precision, and repeatability are some terms that are pretty self explanatory. One that's perhaps not addressed as often is resolution. If I have a scale that tells me how much I weigh and it's 99.9% accurate, but measures only to the pound, then it's inherently low in the resolution department. In a nutshell this means that while it's cream of the crop as far as quality in measuring devices go, it's limited in its ability to measure out in great amounts of decimals. To put it another way, its utility in measuring grains of gunpowder to make a round of ammunition is pretty much useless.

    Remember this?

    . . . . .As a test, I mixed up exactly 32 ounces of new saltwater with Coralife mix and RO/DI water, to a SG of 35 ppt. (1.026 on the refractometer). I then added exactly 8 ounces of RO/DI water and checked the SG again. It now fell dead between 1.020 (27.2 ppt.) and 1.021 (28.5 ppt.). Using the chart below, I took the average of the two and used 27.85 ppt. . . . . ??

    Well, I did the test by adding only 8 ounces of water--but that comprised 25% of the total volume, which was a KNOWN in the experiment. In comparison, when you added 32 ounces of water to a perhaps a few dozen gallons, this was like attempting to measure ounces with a scale that only reads pounds. Get it?

    Your addition of 32 oz. made it nearly impossible to effect a great enough change in variable to measure out your total volume. As far as the refractometer was concerned, you really never made the needle move, so to speak.

    So what does this all mean?

    No method to calculate the volume of water is going to be applicable for all scenarios. You see, it's not always practical to add 5 gallons of RO/DI water to an established reef tank lest we risk killing our inhabitants.

    I'll get back to everyone, as I think the perfect time to try this is before critters are added. My nano is probably the perfect opportunity, as I can add 3 gallons or so, and it will be probably 10% of the total volume. In this way, the salinity will change enough to get a good measurement, and we can apply this method in real life.

    More to come. :)
     
  12. Matt Rogers

    Matt Rogers Kingfish Staff Member

    Joined:
    Dec 31, 2000
    Messages:
    13,466
    Location:
    Berkeley, CA
    Thanks bud... I came to similar conclusions after noodling on it a bit.

    That said, I took my numbers and punched them into your calculator on this site with cubic feet of live rock, sand, etc.. and got a much nicer number. See post above.. and let me know what you think when you have time.

    matt