# New to Reverse Osmosis



## akbar19942k10 (13 May 2018)

Hi guys,

I'm from London and I'm planning to pick up a RO unit from Osmostic UK for my German Blue Rams and Discus hardscape only setup. I'm currently in limbo as to whether to pick up the 3 stage freshwater unit without the deionising chamber or whether to go for the full monty 4 stage unit with the de-ionising chamber.

As mentioned earlier It will be a hardscape only setup so no plants will be in the tank as I'm leaning towards the biotope look, i've also heard plants do not do well in water that has been stripped of it's minerals ect by the deionising chamber and nor do the fish, which brings me to my next querie.

Since RO water needs to be remineralised, to replace the essential minerals that were stripped, i've asked my LFS how they prepare their water for their discus and they told me that they use the 4 stage RO unit, but they cheat. If I remember correctly I was told that they mix 70% RO with 30% tap water instead of using any commercial buffers.

Does anyone else this method instead of using chemical additives to buffer their water and could you possibly recommend me a RO unit to use.

Cheers


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## MattW (13 May 2018)

Hi there,

There are undoubtedly many other people on this forum who know a lot more about RO than I do, I only use it on two nano shrimp tanks and therefore it's economical for me just to buy 25L vats from the LFS every 4-5 weeks, so I won't be able to comment on the RO units themselves.

As far as 'cutting' the water with part tap water and part RO water it's actually very common, I also do this to ensure I'm getting those minerals, as like you mentioned pure RO isn't good for both Flora or Fauna. I guess partly it's personal preference and from what I've read on here many people just suggest cutting with tap water instead of spending (sometimes) large amounts of money on commercial buffers and minerals.

That said do wait out for some more informed responses though, my experience is by no means gospel and the story may be different regarding the fish you're keeping.


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## akbar19942k10 (13 May 2018)

That's exactly what I don't want to do, fork out extra money on minerals and buffers once I've already made a £100-£150 on a RO unit itself. May I ask what ratio of RO to tap water you're mixing to get a rough idea?
Btw I forgot to mention my pH is running at 7.8/8.0.


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## tam (13 May 2018)

Look at your local water report and decide what values you want - then cut accordingly. You basically end up with zero in the RO so it's easy to work out. If the tap water is 20GH and you want 6GH then 30% tap is perfect. 

There is a mix your own remineraliser recipe around somewhere as another option. Or seachem is a fairly popular remineraliser for a commercial brand, they have calculators on their website so you can work out how much you'd use and how much that would cost you over time.


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## ian_m (14 May 2018)

Make your won remineralising agent.
http://www.theplantedtank.co.uk/RO.htm

Though a lot of people just mix with tap water, as it will effectively halve you water cost mixing 50:50.

Just watch and be aware of costs. My water costs, just gone up, to £3.80 per 1000litres. This assuming a rather fanciful efficient RO unit of 1:5 (1 litre RO to 5 waste), that's 6 litre of water required per 1 litre RO, that's 6 * 3.80 /1000 -> 2.3p per litre. Unless you have a pump, you will of course be generally getting worse than this. So a booster pump can work out very good value for money bringing RO units efficiency to probably 1:3 or better.

Oh, and if you don't have a fourth DI unit, remember to dechlorinate (& possible de-ammonia) the resulting RO water with suitable dechlorinator, as RO units are not guaranteed to remove chlorine or chloramine, unless you have a "tip top condition" dechlorinating pre-filter.


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## akbar19942k10 (14 May 2018)

ian_m said:


> Make your won remineralising agent.
> http://www.theplantedtank.co.uk/RO.htm
> 
> Though a lot of people just mix with tap water, as it will effectively halve you water cost mixing 50:50.
> ...



Some sound advide there Ian, much appreciated!

Could I get away without re-mineralising and mixing tapwater without using a DI unit on the RO system or do I still need to cut it with tap water/ re-mineralise regardless of having a DI unit or not?


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## ian_m (14 May 2018)

If you are mixing with tap water you will still need to add dechlorinator, but re-mineralising is no longer needed and arguably a DI unit is no longer strictly necessary.


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## akbar19942k10 (20 May 2018)

So if were to not use a DI chamber in the RO unit can't i just use straight RO instead of mixing with tap water since there will still be minerals in the water as i'm not using DI?


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## ian_m (20 May 2018)

akbar19942k10 said:


> So if were to not use a DI chamber in the RO unit can't i just use straight RO instead of mixing with tap water since there will still be minerals in the water as i'm not using DI?


No the DI unit removes the last traces of minerals let through by the RO unit (and can remove chlorine and ammonia, if your prefilter is poor/used and membrane is failing).

So you still need to mix RO with or without DI unit with tap water (or reminerlising agents).


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