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Discussion Starter · #1 ·
Hello! I have a very irritating issue. My water comes with at least 40ppm nitrates out of the tap. We’re gonna contact the water company as I don’t actually think that’s safe to drink. But I had a question about using it in my tanks.

I was wondering if it would be possible to get an RO unit, and mix some regular tap water with the RO water to bring down the nitrates. As I understand it RO strips the water of everything, making it uninhabitable to freshwater fish. It also drops the ph, which would shock my current fish for sure. I’ve read of people remineralizing RO water to make it safe for fish, but would mixing 50/50 RO and tap have the same effect? Is there any way to bring the ph of that mixture back up to where my fish are at now safely? I have a few very densely planted tanks right now, and they never get below 40ppm nitrates and water changes don’t help. Does anyone have any experience with RO water in planted tanks that might help? Thanks a lot
 

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Hello! I have a very irritating issue. My water comes with at least 40ppm nitrates out of the tap. We’re gonna contact the water company as I don’t actually think that’s safe to drink. But I had a question about using it in my tanks.

I was wondering if it would be possible to get an RO unit, and mix some regular tap water with the RO water to bring down the nitrates. As I understand it RO strips the water of everything, making it uninhabitable to freshwater fish. It also drops the ph, which would shock my current fish for sure. I’ve read of people remineralizing RO water to make it safe for fish, but would mixing 50/50 RO and tap have the same effect? Is there any way to bring the ph of that mixture back up to where my fish are at now safely? I have a few very densely planted tanks right now, and they never get below 40ppm nitrates and water changes don’t help. Does anyone have any experience with RO water in planted tanks that might help? Thanks a lot
You'll definitely bring the Nitrates down. You'll also be dilluting , calcium, mangesium and other trace minerals that your aquarium will need. You can use GH boosters to add the what you need into your RO water. Something like this. Bring it to your desired parameters.
 

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Discussion Starter · #3 ·
Hello! I have a very irritating issue. My water comes with at least 40ppm nitrates out of the tap. We’re gonna contact the water company as I don’t actually think that’s safe to drink. But I had a question about using it in my tanks.

I was wondering if it would be possible to get an RO unit, and mix some regular tap water with the RO water to bring down the nitrates. As I understand it RO strips the water of everything, making it uninhabitable to freshwater fish. It also drops the ph, which would shock my current fish for sure. I’ve read of people remineralizing RO water to make it safe for fish, but would mixing 50/50 RO and tap have the same effect? Is there any way to bring the ph of that mixture back up to where my fish are at now safely? I have a few very densely planted tanks right now, and they never get below 40ppm nitrates and water changes don’t help. Does anyone have any experience with RO water in planted tanks that might help? Thanks a lot
You'll definitely bring the Nitrates down. You'll also be dilluting , calcium, mangesium and other trace minerals that your aquarium will need. You can use GH boosters to add the what you need into your RO water. Something like this. Bring it to your desired parameters.
Does that have any effect on the PH? I’m brand new to the idea of RO water, I always thought it was pretty much a nono for freshwater. If I reconstitute the water with something like that is straight RO water ok to use? I just know that it strips everything that you said and brings ph way down. Pardon my noobness
 

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Does that have any effect on the PH? I’m brand new to the idea of RO water, I always thought it was pretty much a nono for freshwater. If I reconstitute the water with something like that is straight RO water ok to use? I just know that it strips everything that you said and brings ph way down. Pardon my noobness
Nah you're fine. And yea a lot of hobbyists here use remineralized RO water with no problems. Most GH boosters work with just that, General Hardness. You'd have to add something like baking soda to raise KH if you needed to raise it at all. But if you do 50/50 like you're planning to, then replenishing the stripped GH will work just fine for you. Just do some more research in terms of remineralizing RO water and you'll do great. There's some golden ratio to how much calcium and magnesium you'll need in your water, that I have no idea about.
 

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Discussion Starter · #5 ·
Does that have any effect on the PH? I’m brand new to the idea of RO water, I always thought it was pretty much a nono for freshwater. If I reconstitute the water with something like that is straight RO water ok to use? I just know that it strips everything that you said and brings ph way down. Pardon my noobness
Nah you're fine. And yea a lot of hobbyists here use remineralized RO water with no problems. Most GH boosters work with just that, General Hardness. You'd have to add something like baking soda to raise KH if you needed to raise it at all. But if you do 50/50 like you're planning to, then replenishing the stripped GH will work just fine for you. Just do some more research in terms of remineralizing RO water and you'll do great. There's some golden ratio to how much calcium and magnesium you'll need in your water, that I have no idea about.
Interesting. Looks like there’s ways to play around with reconstituting the RO water to the right parameters. I’ll do a ton more research and try it out. Thanks for the info
 

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Interesting. Looks like there’s ways to play around with reconstituting the RO water to the right parameters. I’ll do a ton more research and try it out. Thanks for the info
No problem! You also can get the minerals needed individually and make your own ratios. I use CaSO4, K2SO4, MgSO4 and a bit of CSM+B to boost my tap water by 2 DGH.

I followed the recipe from @somewhatshocked .

CaSO4- 58g / 54.48%
MgSO4- 37g / 34.75%
K2SO4- 11g / 10.33%
MnSO4- 0.16g / 0.15%
FeSO4- 0.30g / 0.28% ( This is where I use CSM+B to get trace elements)
Total 106.46g
 

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Discussion Starter · #8 ·
have you seen any issues with the tank with using the water now?
Nope, no issues. But I’m wanting to dive into some more complex Dutch style scapes and wanna put together an iwagumi tank, and keep some more demanding and particular fish, and I see the excessive nitrates being an issue in all of those scenarios
 

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If you are planning on a Dutch type tank, and going to the trouble to make RO water, then I would just go 100% RO.

Then you can control every single parameter.

And I would not worry about too much about the low pH. Myself and many others use RO with very little to no KH. Unless your fish stock is a known hard water species, most do just fine.

Here's a good article you might enjoy.

https://www.2hraquarist.com/blogs/ph-kh-gh-tds/is-low-ph-in-tanks-due-to-aquasoils-softwater-a-concern?fbclid=IwAR0rqZ5z-6DSDYqeWRT-QB_2U3qFDt79A0U4oc7o21mUYjYIniT27bZ5CQg
 

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if your tap water is already hard, mixing with RO should be fine on its own. My gh/kh is high enough I do 30% water changes with a mix of about 80% RO and 20% tap. I don't add anything. My pH changes by about 0.2 at most.
 

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I have a 30 gallon low-tech planted aquarium and I mix my filtered tap water to RO water 50/50 and that works fine in my case.

I also have some Acid Buffer and Alkaline Buffer on hand as well.

Just experiment with different parts filtered tap to RO to find what works best in your case.
 
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