RO/DI water

[Brianemone]

I've got a new RO/DI unit for my planted tropical tank that should be running within a weeks time, now im also planning on using the water for drinking water as the stuff out of the tap has a horrid taste.

With it being so clean once it passes through the RO unit is there something i can add to it to make it more suitible for regular consumption? also should i be thinking about doing this for the fish tank water before adding?

[Ira]

There isn't anything that needs to be added to it before drinking. It's not going to leach all the minerals from your bones, give you scurvy because it has no vitamins in it or dissolve your intestines or whatever else some people come up with.

[Warren]

Ira's right about the drinking water. You'll need to partially remineralise the water to use in an aquarium or your pH will be wildly unstable. I add the following for every 200L for use on Discus and Dwarf Cichlids:

1 heaped tablespoon of Sodium Bicarbonate (pH/KH buffer)

1 heaped tablespoon of Potassium Sulphate

2 heaped tablespoons of Magnesium Sulphate

1 heaped teaspoon of Calcium Chloride.

From time to time I also add a trace buffer from the LFS.

Because I have a heavily planted tank I also add micronutrient trace element mix and iron chelate's.

Have been doing this for around 10 years now with no problems.

[Brianemone]

Thanks for that recipe Warren. And as per the drinking water thing it is good to see that common sense prevails

[Blackadder]

Why not partially mix the RO/DI water with tap water when using it for your tanks to put some of minerals back. And if you want to add anything for your plants, pH, buffering etc, do it to the mixture.

Seems silly to take all the minerals out then add them again to pure RO/DI water.

[Warren]

I have to as we have 6-8ppm phosphate in our tap water...

There's no choice but to strip everything out just to get rid of the phosphate. I possibly could have used phosphate resins but it's a lot more cost-effective to use RO.

I use 500-600L every week for a water change on my tank so resins get expensive very quickly. It costs approx $40 a year to run the RO ($25 for a 0.5 micro carbon filter and $15 for the membrane). So far the membrane has lasted 10 years. We have no chlorine and very little TDS so the RO isn't working very hard. That combined with the 0.5micro pre-filter seems to be doing the job well. Maybe this combination is why the membrane has lasted so long as you're normally lucky to get 2 years out of one...

[alanmin4304]

How long does it take to produce 500 litres?

[caserole]

It depend on the system you have as to how much you get, mine does 50GL a day.

Warren what does the TDS OR PPM work out to be with you buffering recipe?.

[Warren]

500 Liters takes 5 days to produce. I have no idea what the TDS is after remineralising and it would take me a while to figure it out (would have to look up how to do it now as I can't remember anymore). I do know if water changes are not done within two weeks the pH starts to crash. I'm adding only the bare minimum to keep the pH stable and supply enough basic nutrients for the plants and enough salts to stop osmotic problems in the fish. The water is very soft. You would need to add much more of the salts mentioned earlier to get higher KH and GH for other types of fish.