# Reef tank - Top-off water question



## fishstyx724

I am in the process of setting up a reef tank (a few months in and have 2 fish and various corals) and I have a few questions about topping off the tank. 

-I have heard purified water is the second best option behind reverse osmosis water, is this true?

-Second, if I want to start using RO water what are my options? Is the best option simply to purchase an RO fileter online? I have not had any luck finding RO water at any local grocery stores around here (I live in Chicago). 

Thanks!


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## MediaHound

Hi Scott, 
"Purified" water is relative. How is it filtered? Just running it through carbon is usually not enough, there can still be harmful things in it such as heavy metals and silicates. 

RO/DI (reverse osmosis water then ran through a deionizing resin) is what is most often recommended for a reef tank. It is hard to find at a store. 
Some stores sell RO but its hard to find RO/DI. 

In Chicago you should not have a hard time finding RO/DI water at an aquarium shop, have you asked around any of the stores to see if they sell it? 

If I were you though I would get the equipment and make my own.. I actually personally already do that 

That way you control your destiny and know where the water has been and how good/bad the filter carbon/membranes/resin were that were used, etc..


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## fishstyx724

Thanks! I may just get some from the local store (I think they sell it) and eventually get a filter myself. I am just using purified water from the grocery store, as the people at the store told me that it was the next best thing to RO (will be more condusive to algea growth).


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## GetITCdot

I use an RO/Di unit and in all honesty i love it as the auto-topoff goes straight into the ro/di unit and i need not to do a thing.


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## fishstyx724

Thanks for the input- I've heard of the auto top-off units. So your is connected to or part of the RO filter? What kind do you have?


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## GetITCdot

even simpler then that, I just bought a float valve off ebay, connected it straight to my holding tank output on my unit. shazam


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## fishstyx724

Any reccomendations for RO units? Seem to be a lot out there...


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## GetITCdot

i bought one from craigs list for 70 bucks, its for home use but really any old ro unit will do the trick.


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## fishstyx724

I appreciate the input. I was able to find RO water at a different dominick's my me (midwest grocery store). So I'm good for now, will likely purchase an RO unit at some point though.


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## GetITCdot

fishstyx724 said:


> I appreciate the input. I was able to find RO water at a different dominick's my me (midwest grocery store). So I'm good for now, will likely purchase an RO unit at some point though.


they are INCREDIBLY handy. I also enjoy the taste of RO water.


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## DaynaH9

:fish-in-bowl:


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