RO Filtration

[Greg Curtis]

Can anyone please explain to me what RO filtratiion is and what exactly does it do concerning L catfish. I'm relatively new to plecos and was wondering if I should purchase one or not .Thanks

[MatsP]

An RO filter is basically a filter (membrane) that lets water through, but not ions such as calcium, carbonate, sulfate, sodium, chloride, etc.

What you get out of a RO filter is essentially "pure water". The main purpose is to produce soft water - that makes it more similar to the water in most Southamerican rivers.

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Mats

[Bas Pels]

RO stands for reverse osmosis

Osmosis is a chacteristic where water, with salt, reaches a higher waterlevel than water without salt - wif connectet with each other through a 'filter' such as MatsP described.

However, if the waterlevel on the salty side is increased (salty water is added) the equilibrium is distorted, and a new equilibrium - with more water on the pure side - will settle. Hence 'reverse'.

It requires not that much imagination, that this is a nice way to purify water. The system, however, is very slow, and requires therefore a lot of membrane surface

Further, the salty water will, due to the remouval of pure water, get more salty. Therefore, apart from pure water (or purer water) this system also results in a second waterstream, enriched in salts

[MatsP]

Thanks Bas for clarifying.

I'd also point out that the waste-water to pure water ratio is about 4-5:1 - so for every liter of pure water produced, there is 4 liters of waste-water.

I use the waste-water to continually (more or less) replace water in some tanks with hard-water tolerant fish, and use the pure/soft water for tanks where it's important to keep the water hardness low.

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Mats

[apistomaster]

RO filtration is very inefficient but some fish simply won't spawn or if they do their eggs fail to hatch unless the water is soft enough so the ends often justify the means.
It is also possible in some regions to set up a rain water collection system and filter the collected rain water through high grade activated carbon. Rain water tends to be slightly acid due to dissolved CO2 forming carbonic acid and is good water to use for breeding many soft water species. It is possible to collect quite a bit of rain water if you direct it to enclosed 55 gallon plastic potable water storage barrels.
Rain is free and the barrels and plastic sheets and PVC materials are cheap. The problem with air pollution is often not as bad as one might think and carbon filtration is usually sufficient to remove most undesirable trace chemical that may be find their way into the rain.
I just bite the bullet and waste 80% of the water I run through my RO system. During the winter when the water is in the mid 50's F* the efficiency drops to as low as 0nly about 15% product water.
I use RO mainly for spawning and acclimate the fry to local tap water as soon as I can. Most fish will breed successfully in most tap water and water quality often trumps a particular water chemistry.

Just which catfish species are you hoping to breed? Knowing that would make it easier to give you advice.

[MatsP]

The main reason I use RO water is actually to reduce nitrate that is quite high (in some places as high as 50 ppm) in most of UK - I take it that the nitrate is there due to leakage from farming, but I'm not sure of that.

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Mats

[apistomaster]

Just less than 30 miles away from me is a major agricultural area where wheat and legumes are grown and the communities there also have nitrate and phosphate levels that are on the high side of US EPA permissable levels. I have no such problems.
I always recommend to any aquarists who is beginning to take their water chemistry seriously begin by requesting their water supplier's chemical analysis so you know what the base line levels are for all the parameters aquarists find relevant. These reports are normally free for the asking.

[MatsP]

I always recommend to any aquarists who is beginning to take their water chemistry seriously begin by requesting their water supplier's chemical analysis so you know what the base line levels are for all the parameters aquarists find relevant. These reports are normally free for the asking.

Agreed - and I asked my water supplier for a report - got a PDF a few days later.

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Mats

[Jackster]

The main reason I use RO water is actually to reduce nitrate that is quite high (in some places as high as 50 ppm) in most of UK - I take it that the nitrate is there due to leakage from farming, but I'm not sure of that.

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Mats

I think some people in Iowa and Wisconsin have high nitrate for the same reason, agricultural runoff
that ends up contaminating underground water (wells).

[Greg Curtis]

Thanks guys for all your answers. I think I'll just stick to what I have now until I really need RO.

[DiDi]

When I started my 30gal 16yrs ago a LFS was selling RO water so I asked a bunch of questions, since I have an RO system in my home for drinking water. I started to save Gal. jugs of it so when I did water changes I'd have only RO water. I have a Blue Eyed Pleco named Henry, I have had him from the start and he seems to be very happy in his tank, so for Henry I'd say the RO water has helped him reach the ripe old age of 16.