yay or nay on ro/di? - The Planted Tank Forum
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post #1 of 7 (permalink) Old 05-26-2015, 11:35 PM Thread Starter
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yay or nay on ro/di?

Hi guys,

Just bought a ro di system for my reef tank, but thinking of using it for my planted as well. Tank is cycled with tap so I'm thinking of doing a mixture of tap and ro di.

What are your guys view on doing this? Do you guys see any difference in plant growth doing a mixture?

Aquarium is just going to bee community of angels, tetras and other peaceful fish. High tech co2 pressurized, ferts, the whole thing.

Will ro di help prevent algae growth?
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post #2 of 7 (permalink) Old 05-26-2015, 11:46 PM
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RO is the best for planted tamy parameters are great.. KH, GH, etc.. I'm not sure about preventing algae, but I too have high tech setups and minimal algae in both tanks. The RO water is just super clean and doesn't have all the mineral deposit and dissolved solids that tap water does. I live in the Santa Clarita valley in CA and the water is hard as rocks..

-Mikey G
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post #3 of 7 (permalink) Old 05-27-2015, 12:36 AM Thread Starter
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Should I do straight ro di? Just to?
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post #4 of 7 (permalink) Old 05-27-2015, 01:30 AM
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The first question is: Do you need to?

If your tap water is not right for the fish, then you could do a blend with tap and RO, or go with straight RO and add just the minerals your fish need.

Soft water fish (angels, tetras, many others) thrive within a range of parameters:
GH 1-5 is optimum for many, but a lot of them are OK with GH to 9 German degrees of hardness.
KH similar, if the pH is in the right range.
pH 6.0 to 7.5 is a reasonable range for most soft water fish.
Research your fish. If they need something different, then set your parameters to suit the most particular or delicate fish.

Now, test your tap water.
If it falls within the right range for your fish, they why 'fix' it?
If it has toxins or has unreliable parameters then perhaps you do want to use RO.

Run this test:
1) Make a few blends of RO + Tap.
Perhaps 25% RO + 75% tap; 50/50; 75% RO + 25% Tap.
Test GH, KH, TDS, pH. Make the volume of the samples a cup or two.
Which comes closest to being what your fish want, without going over?
If the GH and KH are not at all similar, then make the blend of water too soft, then add back the missing minerals. If the GH is too low, then add Seachem Equilibrium. If the KH is too low then add some baking soda. Just a tiny bit (or else make a bigger sample, like a gallon or two- the minerals need to be added in VERY small amounts)
2) When the GH and KH are similar, and low, and the TDS is low, the pH might end up in the right range. If not you can lower it by running the water through some peat moss. In this test, just add a small handful of peat moss to the sample and stir it around. Give it a few hours then test, and test again the next day.
3) If the tests make the water what your fish want, and they are stable, then you can go into production making special water for the fresh water tank.

Here is how I did it:
Run RO into a 20 gallon garbage can. 10 gallons. Add 5 gallons tap water. Add knee-hi stocking of peat moss. Circulate it overnight. Add 5 gallons hot water (tap) and dechlor. Circulate a few minutes. This made a 50/50 blend at the right temperature for water changes. The peat moss adds the organic acids that these fish like.
Do water changes.

When you are first changing your fish over to this water you want to go slowly. In any one water change you want to drop the TDS (or GH, or KH) by no more than 10% for delicate fish, 15% for hardier fish. It might take a month for them to acclimate to significantly softer water. If your water is only a couple of degrees of GH or KH too high, then one or two water changes may be enough to get close to the goal.

Top off with RO water.


Last edited by Diana; 05-27-2015 at 01:31 AM. Reason: Added link to very similar thread.
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post #5 of 7 (permalink) Old 05-27-2015, 03:44 AM
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Well, I guess I've made a real idiot of myself and didn't read all the posts carefully enough. Diana's post covers all the material that I was trying to figure out and more. So my post is completely superfluous.

After reading the previous posts in this thread and thinking about it briefly, I think RO has only one good use - diluting hard water to softer water. I am lucky enough to have very soft water, so soft that I have to add Equilibrium to increase minerals. You should be able to test how much RO to add when you're making up water for a pwc to match the water that's already going to be in there by diluting the tap. The GH test kit is probably the way to go. RO is good at making hard water soft. And it's indispensable for reef tanks.

So, it appears to me that that's the way to go to get the water you want. You should probably measure the tap water and the tank water for General Hardness and figure out how much RO you have to add per tap. A gallon of tap going into the tank should require x units of RO to match the tank hardness or the GH you want in the tank - I would drop the hardness slowly, maybe a little less RO in the mix at first, then more the following week. Just to be on the safe side - fish are very sensitive to GH changes.

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Last edited by Django; 05-27-2015 at 04:00 AM. Reason: warn potential readers
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post #6 of 7 (permalink) Old 05-27-2015, 04:13 AM Thread Starter
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I read 20 gh and 8 kh.... So I will definitely be doing a mixture of ro... I will do the testings stated above and see how it goes
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post #7 of 7 (permalink) Old 05-27-2015, 01:07 PM
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So, for soft water species you might find that a blend of about 25-30% tap + 70-75% RO will drop the GH into the right ball park (5-7 degrees), but will make the KH a bit too low (about 2 degrees). Might be OK without altering it, or the pH might be unstable.
Dose with baking soda to bring the KH up just a bit.
1 teaspoon of baking soda in 30 gallons will raise the KH by 2 degrees.

RO is also good when the tap water has something in it that you do not want in the tank such as high nitrates, or worse. It is also good when the parameters of the water supply fluctuate a lot through the year and you want a more stable source for the aquarium.
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