RO Water info needed

[Tommy Saville]

I've been keeping Discus for 7 months, fairly successfully after several teething problems (!), Although I have a very long experience with tropical fishkeeping, I have never come across the need for RO water. I understand how it works, but there are some installation problems regarding fitting a unit and its pipeworks into my system. Info on that is easily obtained, and I'm thinking of installing one,but there are a few stupid questions. For example, is the RO treated water just used for water changes (I'm used to doing 50% of my 2 50 gallon tanks every 3 days, using water from which chlorine, nitrates and heavy metal ions have been filtered out). How much better than my filtered is RO water? If I decide to install it, will a unit produce enough daily for more frequent changes than I do now? Can RO water be pre-heated while stored for changes? Would I still need to do 50% changes as now, or if RO is a great deal better than what I have now would I decrease the proportion? I've seen the term "re-mix" - what's that all about?? And what's DI? So many questions to answer before I ditch my current water-filter system and spend the equivalent of $400 (I'm in UK) on an RO unit.......

[discussmith]

Reverse osmosis units are used mainly as a water softening system. They can remove pathogens, and some chemicals depending on size as they work at the molecular level. Other than if your water contains such pathogens or unwanted chemicals it is only needed if the hardness level prevents the fertilization of eggs in breeding. RO is chosen over normal ion exchange (regular type softeners) resin systems because all these systems do is exchange calcium and/or magnesium for sodium or potasium depending on the salt used. If you have a filter that removes heavy metals you may already be using an ion exchange type system. DI is an ion resin type filter that as a last stage removes any remaining ions leaving the water basically completely void of anything but water. From a PH stand point this water is highly unstable and large PH swings are easily accomplished. This is why buffers are mixed back in to stablize against this. RO water is used like any other water, except it doesn't need to be degassed to stablize PH. It is usually mixed with tap water to add buffer as this is the cheapest way to do that, and with the proper testing equipment you can achieve the hardness level you want. Some RO membranes allow enough hardness to pass through that you don't need to add back any buffer and you can use it straight from the filter.

RO water will not allow you to lengthen your water change routine unless your tap water already contains dissolved organics that require more water changes than normal. Messing with your water parameters is at best a PIA as you risk stability in those parameters. It's difficult to achieve consistency. Discus will do better in water of less than ideal parameters that is consistent than in water of better parameters that are constantly varying.

If your fish have good color, appear healthy and vigorus then RO water won't be needed. If however you feel your fish are not looking their best there may be something unknown in your tap water and RO can make a big difference. It is a good idea to get an up to date report on your tap water from either your water utility or take a sample to a testing facility to find out exactly what is in there. This will help you in deciding and designing a system if needed.

[LizStreithorst]

Why are you considering changing from what you are doing now? Are you trying to breed? If not, you're good to go with what you have.

[Tommy Saville]

Very interesting and informative, Discussmith. Thanks for the input. TDS of my tank water is 168, pH 7.4. Chlorines, nitrates and HMs removed by filters. I have pairs spawning in both tanks (and eating the eggs soon after) and I thought, why not see if I can breed from them.(if only to avoid the battles that occur when the pairs are guarding the eggs for a couple of days !). I'm fairly sure the current water params are unsuitable for breeding so maybe I should instal RO.But I know so little about what is involved, hence the question. Otherwise, the fish look healthy in every way, despite the water not being absolutely ideal. I have an empty 20" cube tank.