Reverse Osmosis

mikejp67

Can anyone explain to me the pros and cons of useing water from a reverse osmosis for a fresh water aquarium?

Byron

RO is used when there is something in the source water (presumably tap water, but can be well water) that you don't want. Minerals that cause hard water is the usual issue, if one wants to soften the water for instance.

The problem with RO is that is literally removes everything, so you are left with very pure--but very un-natural--water. Water like this does not exist in nature because water is a powerful solvent, meaning that it takes up in dissolution almost everything it comes into contact with. Depending upon the fish (and sometimes plants) in the aquarium, you need to either mix the RO water with some tap/well water, or add properties (usually minerals, but perhaps tannins) to it.

It can also be expensive. Running tap water through an RO unit is slow, and most of the water is wasted. The resulting RO water is less than the initial volume.

I think that explains it simply. If you have questions on why you may need it, if you think you do, we may be able to suggest alternatives.

mikejp67

Thanks Byron for the info.

AbbeysDad

Byron is correct, RO forces water through a very fine membrane and filters out dissolved minerals. Systems often also include activated carbon to adsorb chemical impurities. Some systems also have a deionizer (DI) filter with scavenger resins to further remove unwanted elements.
RO systems typically require a constant 50psi water pressure to force water through the membrane. This is higher than many/most well systems which would require a booster pump. RO systems also discharge as waste approximately 4 gallons of water for every gallon of RO water produced.
I have very high nitrates in my well water so I opted for the much simpler API Tap Water Filter to produce DI water. It includes an adapter to connect to most faucets (replacing the aerator). Like RO water, it also must also be treated to add some minerals back and adjust pH. The downside is that the filter cartridge life, as one would expect, is relative to the impurities in the water. The filter cartridge changes color as it slowly exhausts. I'm not quite finished with the first cartridge yet but it is nearing the end after 55 gallons. (filter cartridges cost about $25).

The only reason to consider RO, DI or RO/DI water systems is if you're serious about the hobby AND have a known bad condition with your water. If you have good tap water (and provide good tank filtration) you should use it and it will be fine.

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