Switching to RO water - The Planted Tank Forum
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post #1 of 5 (permalink) Old 04-01-2017, 11:41 PM Thread Starter
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Switching to RO water

Hi, I have a planted 40 gallon community tank (Guppies, Neon tetras, Corydoras, Otos, Amano shrimp) & a planted 10 gallon tank with RCS, young Amanos & 3 young Bamboo shrimp, I'm going to start using RO water because the tap here is very hard. So should I mix it with the tap or just add it in to the tank? If just adding it in would I need to remineralize it now or when I get it to the KH/GH levels that I want? More info: I'm trying to lower the ph (8), KH is 14 & GH is 7 of the shrimp tank. Thanks.

Last edited by harley; 04-02-2017 at 12:56 AM. Reason: Ph level
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post #2 of 5 (permalink) Old 04-02-2017, 07:21 PM
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I use RO water to drop tds in my shrimp tank as I have CRS, in turny fh and kh also has dropped :-) I just add tap water to my ro water yo get disired tds. Same thing would kinda apply here For you

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post #3 of 5 (permalink) Old 04-02-2017, 07:36 PM
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You may want to invest in a tds meter, about 20 bucks on amazon or [Ebay Link Removed] Does your unit have DI or is it just RO? Mine is just RO and the water has enough minerals that I can simply add it to the tank without altering. ( I have super hard tap water)
If yours' is just RO, you may find that the tds and parameters are ok right out of the unit or may just need a little tap water added.
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post #4 of 5 (permalink) Old 04-02-2017, 07:59 PM
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RCS and Amanos seem to be fine with hard water. But it is your choice and targeting a good GH and KH is not hard and might help with your neon tetras and cories.

I would say, start by doing only small (20%) changes until you reach your target GH, your KH might still be a little up. At this point start remineralizing the water, target optimal parameters for the volume of displaced water only. Larger water changes can be done now. Your KH, GH will stabilize in time. You can of course mix RO water with tap and until you get your target. Since your KH is double your GH, I would set my RO-tap target for a certain KH and then add some extra GH boosters ( Salty shrimp GH+ , Shrimp King Bee Salt , Nilocg GH Booster etc)

As others mentioned, once you have your mix % set for a certain GH KH you can check with your TDS meter. Afterwards, reaching the ~TDS value from the same mix gives you a fast and cheap confirmation that everything is good, without the need to test GH, KH every time.

A RO unit with functional membranes and filters should give you a TDS < 10 , not much can be in such a small TDS

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post #5 of 5 (permalink) Old 04-02-2017, 08:23 PM
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This might call for adding some acid. I'm not sure what to add or how much to add or how to go about it safely but would love to find out. I have seen it done in a lab on Youtube. It's really easy too add too much acid. The guy in the lab had a problem with that so be careful if you decide to try it.

Your current 7 dGH is about 125 mg/l CaCO3. To lower it, subtract your target mg/l from your current mg/l and divide by 125 mg/l. This is the percentage RO water to add to your mix. Don't lower your GH precipitously because this could cause osmotic shock and injure or kill your animals. 17.9 mg/l CaCO3 = 1 dGH.
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