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· Registered
140 Posts
Discussion Starter · #1 ·
From what I've read in the forums RO water needs to have its GH and KH increased for a myriad of reasons. Equillibrium + baking soda or RO Right. I get this part.

My question is, Does RO water need anything else? Like trace elements from a plant food or SeaChem trace etc? Is there anything else I'm missing?

I'm staring a new tank at my house and the KH is is 20+ and PH above the high range test. Since it's only a 5 Gallon tank RO isn't going to kill me. I'm not planning on keeping anything fragile. I'm just looking for a good starting point for neutral water where the PH won't jump around.

I'm not using CO2. Just a boring old planted fish tank.

· Banned
5,927 Posts
Then just change 1 g per week and add back 1g of tap + 20 z of the RO and you need nothing else. This will give you a Ph of 6.8-7.2 after at least 5 water changes and it will stay there after that as long as you change 1g per week and add the 20oz of RO each time. When changing, add the RO first and measure it in measuring cup fairly exact. Then add the tap in case it's too much that you can't add all of it.
This will also bring down the KH to a reasonable amount.
Just remember your local fish store likely has the same water you do in their tanks.
So you would be wise to drip aclimate the fish before putting them in your tank.
Really a tank that size is mostly just good for shrimp. Or like one Betta.

· Registered
100 Posts
what type of fish do you have, determines your KH/GH

plants will thrive with your 100% tap water, along with weekly water changes.

· Registered
11,717 Posts
Get a gallon of RO water.
Blend Tap + RO until the mixture suits you and your fish. GH, KH, TDS, pH.
Tap water may have some minerals, but probably best just to count on it for Ca and Mg, as long as the GH is 3 degrees or higher.
Fish (or shrimp) food may supply N, P and most traces.

I would plan on dosing K and Fe. The simplest is with a liquid product called Leaf Zone. For a 5 gallon tank I would not go overboard with dry ferts.

Of course when you really get addicted to this hobby...

· Registered
140 Posts
Discussion Starter · #5 ·
Thanks for the tips.

The plan is for shrimp as well as some other smaller fish species. I'm guessing even hard water loving fish probably don't like 20 drops.

I'm more interested in the things in Diana's post. Items like N, P, K and Fe all get stripped out and I was looking for info on how and if to get them back in as well as any other products that could be helpful.

As for my tap water. I'm in a neighborhood out in the country that gets its water from a well / water tower system. I'm not sure if they add trace elements or it's straight from the ground. Other than hardness at 20 i'm most concerned about silicates. At my work tank I'm fighting diatoms and would prefer not repeat if possible.

I'll look up Leaf Zone.


· Registered
11,717 Posts
So here are two ways to get the answer:

Set up a 'tank' (ie bucket, whatever) with the blend of RO + tap that suits your livestock.
Feed it just like you really had shrimp and fish in there.
Test with all the tests you have or can find.
NO3, P, K (maybe- I understand they are not worth much), Fe, GH, KH, pH, TDS
See what a non planted tank is like. See how these values rise through the week.
Then add a handful of plants. In a 5 gallon bucket I would have a couple of gallons of water and a double handful of hornwort or anacharis. Put a drop light over it. Maybe a glass lid or a screen to make sure the drop light does not drop into the water.
Continue feeding the virtual fish for another week or two and see what happens to the tests.

Here is the better way:
Set up the tank the way you want.
Cycle it, or at least add some nitrifying bacteria (Nitrospira species).
Add the more durable of your livestock.
Run it, seeing what happens. The plants themselves are your 'test kit' for many things.
I would test TDS, GH, KH, NO3 and maybe pH. Of course a new set up would need NH3/NH4 and NO2 tests until the cycle is complete.

When the tank is up and running, and the cycle complete:
Use the NO3 test as a stand in for N, P and traces.
If the fish food is supplying enough NO3 (it stays between 5-20 ppm, or else you have to do water changes) then you can assume the food is also supplying enough P and traces. (but not Fe)
If the fish food is not supplying enough NO3 (it keeps dropping, or barely shows up) then you can assume you need to dose NO3, P and traces.

Use the GH test as a guide to Ca and Mg. Unless you have a reason to think the Ca and Mg have a weird ratio out of the tank, assume that a GH >3 degrees and stable is just fine. If you think there is an odd balance from the tap water between Ca and Mg, then you will have to get a fresh water Ca test and figure it out.

Use the KH and pH tests to know that things are stable. I generally set the KH pretty much equal to the GH, then the pH is controlled by the carbonates or peat moss in the right range for the fish.

Use the TDS to know if salts and minerals are building up, and as a clue for a water change. Whatever they are to start with (you decide by blending RO + Tap water) you can see the changes over time. Usually the TDS rises, and you will do water changes to keep it stable.

Assume you will need to dose K, Fe and C. There is generally not enough K or Fe in fish food, and carbon is almost always needed, even a low tech tank can benefit from some carbon.
The plants will tell you about K and Fe. Look for pictures of deficiency in these 2 elements so you can see the earliest signs.
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