karen b asked in PetsFish · 7 years ago

For a reef fishtank, is it better to use old RODI filters or plain tap water?

My reef store is out of filters for my RODI unit right now and I really need to do a water change. My TDS meter is reading 0 ppm going into the Meyer, but 11 ppm comming out of the meter, which I believe means that most of my filters are good but the last stage filter must be bad.

How bad is a TDS reading of 11? I have spa, LPs, and soft corals. Oh and I am filtering well water.

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  • 7 years ago
    Favorite Answer

    depends, most tap water is ok but obviously RO is better as long as you build up the alkalinity etc. with a good salt mix and supplements.

    don't know about your well water or whether anything is particularly bad about it...

    not sure what you mean by "going into the meter"

    TDS is a measure of all dissolved solids and I'm not sure why you'd have a higher reading coming out of the filter, (assuming you meant filter, not "meter") even if the filter was bad. But I don't think a reading of 11 is anything to worry about necessarily, depends on what's causing the reading.

    I'd use the water coming from the RO even if it's in need of filter changing, has to be partially filtered at least. And you'll use a little Novaqua/StressCoat/Prime anyway to detoxify any copper/metals etc. in the water....

    edit: again, I just don't know what the dissolved solids in your water are. If they're agricultural runoff, then that's bound to be bad, if it's salts of some sort, then it's probably just fine.

  • 7 years ago

    Good tap water can have a TDS of 200. So 11 is still much better. Do not use tap water.

  • ?
    Lv 7
    7 years ago

    I use RO water in my Reef tank my tap water has Nitrate in it and as Nitrate has to be 0 in a Reef tank i would never use tap water .

    Can you buy saltwater already mixed or RO water .

    I used to buy RO water from a local Aquatic shop to top off and when i was feeling lazy Salt water already made up .

    I would not use tap water based on that reading

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