RO Water and Its Benefits for Fresh water Fish setups? - If any

Hi Every one in Fish Land,

I am sure this has come up before and I apologies in advance if it has, but I did search the forums and did not really find anything much on this topic.

Has anyone got some information or first hand experience or opinions on the use of RO water for Fresh water setups. I know this is a widely adopted and used option in the Salt world, but with the advent of the new fresh water shrimp craze and interest as well as more sensitive fresh water species that are becoming popular in the hobby that have never or rarely been available in the past, like rays, puffers, etc... I was wondering if its a viable option.

RO units and water purifiers are readily available these days in and in most cases cheaper than a really good canister filter.

Yes I know their is always the argument that it uses a lot of water and can be expensive to run, but then their is also the argument that the waist water can be used in the garden or the swimming pool, especially the swimming pool since you are dosing with chlorine anyway, so then generally speaking their is no waist.

Information on the internet is a bit sketchy at the moment on this particular subject and at times very conflicting.

Perhaps some of the more chemically educated members can chime in on this!

Bottom line I guess is, does it do more harm than good or more good than harm!

 

I was contemplating this very issue earlier this morning.
I am considering the use of RO water to soften the tap water for my German Blue Rams.
Our tap water seems to be buffered at a pH of 8.5, which is on the high side for fish.

To breed the GBR I would like to lower the pH even further, to between 6.5 and 7.
A stable pH is better than trying to juggle the ideal RO and tap water combination, but if I can get stable results by adding say 5 litres of RO water to a 3ft tank, it would be worth it.

Our local LFS has RO water available at a reasonably good price.
In terms of savings, I would have to use RO water weekly for 118 weeks, or over 2 years before I covered the cost of a basic RO system.

Whether RO water will have the impact I desire, is debatable however.
I am also looking forward to any answers forthcoming.

 

The advantage of RO is that there is nothing in it that you didn't put there so you are able to control your water parameters exactly as you would like them. You will need to re-mineralize the water as RO will have no buffering capacity and will be prone to pH swings. Also probably not that healthy for your fish to live in unmineralized RO water - just thinking of osmosis of minerals from the fish to the water - although I haven't tried keeping fish in this way before.

 

Would RO that was mixed with tap water "take on" the minerals and other things in the tap water?

I started measuring the pH and temperature over the last few days.
Temps and pH remain consistent, even though water changes are done and chemicals are added daily.

Day °C AM °C PM pH am pH pm Excel Ferts
10 22,6 24,2 8,1 8,1 1,0 1,0
11 22,8 24,2 8,1 8,1 1,0
12 23,0 24,2 8,1 8,1 1,0

Would the addition of 10% RO water per volume of a tank weekly lower the pH slowly, and then stabilise, or cause pH swings?

 

Ahh the double edged sword of RO.

Let me start with my own experiance and uses for RO water. RO water should have a neutral ph of 7 and tds at 0 ppm, giving you basicly pure water with 0 buffering. Ok that is how I understand it.

I only use ro water in my 2ft crossband chocolate gourami tank. Reason for this is that I have to keep the tds belowe 50, normaly between 30 and 40. Now at this low level of tds you will get a ph crash, ask any discus breeder how ph can change from 7 to 3 overnight. Because of this I have to use a substrate that buffers the ph to 6.2. Without this I will have no controle over the ph.

You can use ro water in other set ups but you will need to add some form of buffer to the water to keep it stable at a certain ph, kh or gh. In my personal opinion this is not worth it as you will constantly need to check you aquarium and water for wc to make sure they match.

For a normal comunity tank I will not bother with ro as it can do more damage than good. I'm sure @MariaS can supply some details on her ray tanks, which I don't think she uses ro water for.

In the end there is the waist part. I buy my ro water directly from my lfs. I use between 20 and 30 L per week for wc so I have no idea what the actual waist is. If I remember right ro units only gives you about 1/4 of volume used, leaving you with a lot of waste in the end. In my case it's between 60 and 90 L per week. Now imagen your doing a 50% change on a 4ft tank. Can puch you water bill up by quite a bit. I know there is ways that you can re-use the waist for swimming pools, flushing toilets, watering garden etc. But you will have to store this water for when you can use it in the end.

Ok a lot of rambling from me. Can't stop when I start, sorry. I realy hope some of the other members will share their good and bad of ro.

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I have been using purified/filtered water on my tanks for nearly a year now.

Started this Sunday with water changes of 25% of unfiltered tap water for the following reasons:

• Some plants don't do well and slowly fade away due to lack of minerals and trace elements.
• The pH of tanks became dangerously low, had to use crushed coral to boost tanks for a week before I could add tap water to avoid pH shock.
• Long term exposure to demineralised water cause immunity issues and fish are more susceptible to parasites and diseases.
• Filtered water will only be dechlorinated as long as the carbon filters remain effective, lost livestock due to under-dosing dechlorinator when chlorimines where very high.
• Fish seemed tired and lethargic, became lively and active when started using tap water again, problem now is to get their appetites down cause they are destroying my plants xD
• Experienced issues when introducing new fish from lfs due to different water parameters.

Bottom line is that there may be advantages to using filtered/ro water, but the remineralisation of water and frequent water testing was time consuming.

Normal tap water is quicker and may be healthier for the tank occupants in the long run.

Note: Above-mentioned was experienced with water in Pretoria area and may not be applicable in different geographic areas.

 

RO water will not lower you pH as you need to introduce H+ ions to reduce pH. RO water is normal water, just without buffering capacity - meaning that the pH can be altered more easily than tap water.

The minerals will still be there - their concentration will just drop by the proportion of RO to tap water.

 

Thanks for the input.
It seems at the end of the day that the use of RO water is more of a hassle, than worth it.

 

Thanks for the info @TheGrissom, that is a very interesting piece of information. So if I understand correctly RO water could be quite beneficial in certain instances where you need say a specific pH and then perhpas you have quite unstable tap water with pH fluctuations all over the place, then RO water in the correct ratio to tap water could stabalize this?

In general if I understand correctly overall if you can get the ratios correct you have a better chance of been able to succesfully alter the pH of the tap water either up or down and keep it pretty stable with RO.

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yes RO water allows you to more easily alter pH and to get exact water parameters but it is also more work. Tap water is good enough for most species and is itself pretty stable but you have to accept what you get out the tap.

 

I have been thinking about this. Personally I feel unless you are a breeder looking to breed a particularly difficult species of fish it probably isnt worth using RO water. If you want water that is softer than tap water then mix rain water and tap water (its easier and cheaper than RO) but you need to ensure that your rain water is not polluted. My rain water at home has a tds of about 30 which is very soft - the only down side is that I do not know what is contributing to this tds - it could be anything soluble really.

 

The issue with rain water in Gauteng is that it is probably so full of pollutants that you don't want to risk adding it to your tank.

I am still trying to read up about the effects of mixing a 10%/volume RO with normal tap water.
As soon as my TDS pen arrives, I will test the various combinations, and see what it does.

 

Also did a lot of reading on this and am still considering a dedicated RO setup. It really depends on what fish you intend to keep - as others say, tap is totally fine for most purposes. Its naturally important to establish all water parameters from your local tap water as a starting point - and then see which fish would be happy in it - or rather, which 'finicky' fish wouldn't.

I use store bought RO only for my small ram breeding tank, mixing a set amount with tap at every water change. I keep a careful eye on KH - when that is low, without buffering capacity (so 0 KH), then PH swings occur.
That however happens when nitrate levels start getting high, then becoming a concern. Because I do frequent water changes, with low bio-load fish, nitrates stay low, and my KH of 1-2 isn't a problem, and PH is stable.

As mentioned above, RO is great for keeping within a targeted TDS range, and is primarily why I use it. Also, we have had fluctuating PH and TDS in Cape Town lately, throwing a spanner in the works and necessitating more water testing and making a bit of a case for RO and manual remineralisation.
With RO having a PH of +-7, that will also need considering when using it, depending on what your tap PH is and the PH your fish are happy in.

 

Have been dabbling a bit with this exact thing. Mixing and matching RO and tap water. But I have just been "playing" with it to see the effects on one another with a TDS pen. This weekend I intend to do some "real world" slightly more scientific experiments with mixing, but will this time properly record the readings etc.... at the moment I am running a very small short term experiment with brine shrimp and RO water. Set it up last night identical to my last one i did with tap water. Same salt, same salinity and same batch of eggs, with same lighting and airflow.

 

Less than 24 hours and the brine shrimp hatched already. And this time I got a slightly better yield using RO.

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So I just did a couple of multiple pH tests between some RO water and one of my tanks and all the tests show that the pH is 7.4 also tested my tap water and its the same.

Possibly my "cheap" Daro pH test kit does not give accurate results. Currently I dont have options to test water hardness yet.

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Is it test strips? The best way to test the pH of RO will be by chemical means and an indicator.

 

Unless you are going to play mad scientist and get some good quality digital test gear, RO and trying to get the mix just right is going to be a pain - well at first.

Have you clearly qualified why you want to go RO?

Later Ferdie

 

Nope okd fashion bythomenyl blue 2 drops in a small vial. I was thinking of trying to use HtH pool test strips as a comparison.

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RO should be around PH 7 - with TDS under 20 usually (I assume a 5 stage or more would be 0).
In my testing its always been around that number, just using liquid test kits.

I don't understand the chemistry behind our local CT water having very low KH (and GH) but with a high PH of 8+. Would be interested to know if anyone can explain!