Moving To RO Water - Would Appreciate Some Advice On Figures.

Hi folks,
I am moving over to RO as my tapwater is poor for South American Cichlids and I want it in the softer range to try and keep some future purchases happy (Plecos)

I have now got the RO unit hooked in and have done some testing.

While I was at it, I plumbed in a dual TDS meter to monitor TDS in and out and added a couple of taps to halt flow should I want to.



My TDS into the RO unit:



My TDS out of the RO unit:



Ive installed a water butt to collect the RO and am on with planning a pumping system to end my days of carry buckets, but thats another topic.



So.. On with a long night of testing...



I tested the tap again.

PH - 7.4
KH - 107 (6d)
GH - 179 (10d)
TDS - 209

And tested my RO.

PH - 6.4
KH - 0
GH - 0
TDS - 8

My first test is 50/50 as thats the simplest option and doesnt as far as I can deduce, need me to mess about remineralising it. That mix gives me.

PH - 7.2
KH - 53.7 (3d)
GH - 125.3 (7d) (Surprised this ddnt half?)
TDS - 102

I am reading in some places that a KH value under 4dh will give me unstable PH. Not sure what to do about that. Will have to try a different mix first of all, but if the magic number is 4, how close to 4 can you hover safely? Im reading on forums that some people are very happy and stable at 3?

Im tempted to run 100% RO and remineralise it to exactly what I want. First of all I guess I need to settle on a figure that I want. At the moment, with an unstocked tank thats proving pretty tricky, especially with all the conflcting advice out there!

Ah well... im committed now, got to look after my boys.





Any advice anyone can give me with regards figures to settle on for South American Cichlids and some Plecs would be VERY much appreciated. Along also with your chosen route to remineralisation and the products you personally use with success.

I have soft water here in Wales with the tap water testing as GH 6º and KH 3.5º

I do all the things that I shouldn't. I have DIY CO₂ which brings the pH down from 7.4 to 6.6, I have two lumps of bogwood, I'm 75% stocked in a 55liter tank (but I use oversized external as the filter 'cos the AquaNano 40 has a massive built-in filtration unit), I've got a peatball in the filter and use Indian Almond Leaves.

However; I do 20% w/c each week and test my water's pH regularly and it's very stable at 6.6

The one thing I do know is that you need to lower the hardness slowly. The easiest way is just to do smaller more frequent water changes with your chosen RO mix. That will reduce everything a bit at every water change till after a few changes the tank will be at your chosen level.

You'll probably be OK aiming for the top end of the altifrons' range. Fishbase doesn't give a hardness range for altifrons (when it does, I go by that site rather than Seriously Fish). But if yours are OK in your hard water maybe you could get away with slightly harder water than SF gives, but not as high as the upper level for the redheads.

With my water I have no need for RO so all I know is theoretical. To be honest, unless your tap water is absolutely horrendous, mixing tap and RO should be fine. The danger with using RO is running out when you need to do an emergency water change. As you have your own RO equipment that shouldn't be a problem, but make sure you always have a stock of things that need replacing (membranes?). If you were to go down the 100% RO + salts route, you should always have an unopened pack of salts in the cupboard. And using salts adds to the expense while tap water doesn't.

Your water changing regime sounds fine. I didn't want you to forget that you can't make a big change all at once. You probably knew that already but I needed to state it for anyone else reading the thread who didn't know.



Fishbase is a group of mirror sites written by and intended for use by scientists. As such it doesn't often have fish keeping data (eg what size tank, how many should I have) but it usually gives temp, pH, hardness requirements and size. It is the most reliable site for those stats.
However, it doesn't always work. If that happens, just try one of the mirror sites at the top of the page, they are all in English.

Thanks Simon and Sue - you have put my mind at ease.

The first 50L of 50/50 has gone in and I will just carry on as I am now and see what happens. Might have to pop out shopping on Sunday and see if I can find some suitable tank mates... it is fathers day after all.