RO water & Top Off's

Discussion in 'Water Parameters and Additives' started by Nemos Janitor, 17 Mar 2010.

  1. Nemos Janitor

    Nemos Janitor

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    The use of low TDS RO water is often recommended as top off water for salt water aquariums. The thinking is that only the water evaporates leaving behind the salts and TDS. Not 100% true. A simple TDS test of the evaporated tank water will prove. However the salts evaporated are so small it is not worth the argument. The reduction in aquarium water volume necessitating top off is not only evaporation. We have skimmers that remove skim mate, Overflows that splash, Algae scrubbers that are harvested etc. These forms of water removal also remove salts and TDS (trace elements/minerals).

    RO water should periodically be checked. If the output from the RO unit is high then the unit needs to be serviced. (waterboy will best advise here) However good RO water that is made needs to be stored in an inert sealed container. Pure RO water is very susceptible to contaminants and will absorb these from the air or any surface it contacts. Also while RO water is believed to have a pH of 7 it could in fact be as low as 5 due to excess dissolved CO2.

    Considering the above, the top off of pure RO water into a tank has a few concerns. Whilst the addition of RO water via a level switch and solenoid connected directly to ones RO unit will have very little impact on the aquarium chemistry i caution this approach. All it takes is for the solenoid or level switch to malfunction and a flood and washed out aquarium is the prize. Naturally salinity needs to be monitored and salts and additives dosed as required.

    Top off systems that replenish on a max min basis, manual or automatic, best require the RO water to be treated first especially when 20 odd liters are added. This is to replace the used salts Ca etc. Products are available for this.

    Another way of top off is to drip Kalkwasser/RO water at the rate of water usage. A simple saline drip available from most pharmacies attached to a container will do the job. This method only adds calcium. But it does limit pH and Kh swings.

    Another method is the bailing system. Very similar to the above. But a very efficient way of adding a balanced calcium. I will not go into the details of the bailing system as that is another thread on it's own.

    I think i have covered my view on the subject and please feel free to add or comment.
     
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  3. chikaboo

    chikaboo

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    I noticed this the hard way last week and I stand to correction as to who pointed this out (I think Marc mnd) but I hadn't checked my SG levels for a long time and was shocked at how low they went..... I didn't bother because everything seems fine in the tank but I think the drop in salinity was so gradual and the total water volume counted for everything not being affected - all livestock seemed to adjust nicely - but a few more months I'm sure I would be experiencing problems ....
     
  4. Singularity

    Singularity Hmmm amper!

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    What products would you suggest ?
     
  5. Nemos Janitor

    Nemos Janitor Thread Starter

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    We use Tropic Marin re-mineral marine. But other manufactures like Kent and i think seachem have them. Julian Sprung (Two little fishes) recommends using his two part calcium mix. I am sure some of our sponsors have products suitable.
     
  6. Singularity

    Singularity Hmmm amper!

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    like the one seachem product that can only buffer up to 8.3 even if overdosed ? Cant remeber the name right now
     
  7. mandarinman

    mandarinman

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    wouldnt a bit of aragonite in bottom of ro top up container correct ph every time cos if it is really low aragonite will dissolve and buffer?(just me scheming again)
     
  8. Manic

    Manic Moderator

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    Don't think the RO water will provide an acidic enough environment for the aragonite to dissolve that quickly to provide sufficient buffering capabilities...
     
  9. Nemos Janitor

    Nemos Janitor Thread Starter

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    Not if the pH is above 6.5
     
  10. dallasg

    dallasg Moderator MASA Contributor

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    brightwell have Alkalin8.3 that i use
     
  11. TheWaterboy

    TheWaterboy Sponsor

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    we have a clip on kit for our r.o.units that has tunze / seachem (which ever you prefer to use) calcium carbonate in them......with a tweak the r.o. water can reach down to as low as 6 and dissolves only calcium into the water thus buffering whilst topping up

    with testing i recall we had o t.d.s comming out the r.o.unit with ph 6.4 then 15 ppm to 18ppm of calcium carbonate after the clip on chamber with a ph of 7.5
    :thumbup:
     
  12. IMarine

    IMarine

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    Excellent info bra
     
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