REVERSE OSMOSIS FILTERING

Hi everyone, has anyone here used this method in their aquariums. Are there any benifits? Regards

No such think as reverse cosmosis. There's no C in osmosis. Also you shouldn't use it exclusively in freshwater, it's only regularly used for topoff water for marine tanks.

I once used pure water - filtered, demineralised - for doing water changes on a 3 ft tank for a couple of months. It caused quite a few problems with different algae which I couldn't get under control, and unhappy plants and fish. I ended up spending a lot of time trying to correct the water chemistry by adding various things until reality kicked in for me, in that I was putting a lot of effort into a mediocre looking tank.

I wouldn't recommend it, if you have access to reasonable tap or ground water use that. From a simple perspective - natural water isn't pure. It runs over clays, rocks, various other rubbish, and picks up minerals and salts.

You can use it but have to use a trace element or mix it with other water to get your required mineral content.

For fresh water the only real benefits I can think of are

complete control over what goes into your tank (which is very rarely neccessary)

provides very soft water, which maybe helpful for some fish, for example breeding discus. But rain water can work just as well.

if you have a poor water supply and are worried about bacteria, heavry metals etc, in which case you should look at having one that does your drinking water to.

I've heard that exclusive use of RO water can upset the isotonic balance of fish as RO water is very pure and has had all minerals, salts etc stripped out of it.

RO/DI water is only good for marine aquariums I think. This is because the chemistry of natural tap water changes periodically, and this change can 'shock' sensitive reef animals such as anemones, corals, clams, etc.

Remember RO/DI water has none of the minerals etc that comes with non RO/DI water. There is a big debate on wether or not it is healthy for humans to drink RO/DI water due to lack of any minerals.

Just to clarify, RO/DI is used in marine tanks for a few reason. But mainly because corals etc are very sensitive to a lot of the heavy metals from commonly in tap water, particularly copper. Since RO/DI water is used to topup evaporated water the levels of heavy metal build up if you don't use filtered water (cause the heavy metals don't evaporate).

With regards drinking RO/DI water, it is no different from the pure drinking water you buy from the super market (in fact some small marine tank owners just use supermarket water), and a lot of the better under sink water filters are RO/DI. I think the myth was just started my reefer's to stop their wife's from wanting to drink their topup water supplies. :bounce:

and if your pure water caused all sorts of algae growth, it wasn't very pure.

and if your pure water caused all sorts of algae growth, it wasn't very pure.

Topping up a well established tank with demin water only certainly caused some odd algal "flushes" as the various minerals ran out of balance. I'm pretty confident the water was clean as I was "obtaining" it from a very precise industrial process which couldn't tolerate impurities in the water supply. I recall going through phases of one algae dominating, then dying off suddenly. If I'd taken notes it would have been an interesting experiment. I recall staghorn, hair algae, green water, green dot algae all dominating for a short period, then being displaced.

I always presumed that as the various minerals held in the gravel and so forth in the tank were exhausted, as as each condition changed a different algae dominated until it hit it's specific growth limiting factor.

ok, i'll slither back to the Dark side.......

Its interesting that in marine we spend alot of time and money getting rid of nutrients and dissolved solids/minerals to reduce algae growth.