no more w/c ?

[G-1000]

Is it possible to have like a 6 foot tank with a reverse osmosis unit hooked up to a canister or something similar to constantly filter the water?

say you have a 650L 6 foot, which has a 160L per day RO unit - would you ever need to do water changes again ?

Do you get me ?

G

[madaboutfish]

Over time wouldn't the water be too pure which will ultimately kill the fish?

Nick

[nicholas76]

yep !

i believe you would have to add minerals back into it!

[wickedglass]

the problem with R/O units in this sort of scenario is that there are all sorts of things that will build up in a tank that will not be filtered out by R/O or a canister filter, like proteins, nitrates and certain oils. In tanks which haven't had water changes for a long time you can see surface layer of these oils and proteins. In marine tanks these proteins can be taken out or skimmed with the aid of a protein skimmer. These units work because of the density of the salt water ... freshwater isn't as dense so those don't work.
It is possible to have a large tank with minimal filtration and no waterchanges, and I've seen such tanks when I was a kid in the 70s. But all such tanks had a huge amount of plants in them and a minimum amount of fish. The tanks had been running for a long time and the amount of fish had been balanced to the amount of plants. The problem with those tanks was that you hardly ever saw the fish.
In the early 1770s a guy called Joseph Priestly discovered that plants produce oxygen. In the early days of the aquarium hobby (around 1850s) it was believed that a closed and balanced system was the way to go. No filtration or heating. Some substrate, lots of plants, a snail colony and a few fish were all that were needed to create such a utopian biotope. This was a principle still practiced in the 1970s by my father's master, and those are the tanks I saw. But since the 70s the aquarium hobby has advanced in leaps and bounds. Scientific research, and that of private hobbyists has again and again proven that there is such a thing as water that is too old. R/O units will take out minerals and some other contaminants, soften the water, but won't take out waste proteins and nitrates. neither will your canister filter. plants will use those to grow, though.
I guess the bottom line is that the ideal of a virtual perpetuum aquarium with no w/c is a dream which may work, depending what you aim to achieve ... if it is your aim to purely achieve something that will need no water changes, then that is a possibility ... personally I wouldn't bother, though because the act of changing water proves time and again that water which is fresh and rejuvenated is good for the fish. It induces them to be more active, show more colour and in many cases even initiate spawning activities. Think of it this way, yould you drink water which was distilled out of your own pee and be happy about it? :P

[G-1000]

Yeh good point.

I wasnt thinking like in terms of me being lazy - but more so that the fish have a constant supply of fresh water.

A large planted co2 tank is clearly the best choice.

G

[taksan]

A R/O unit won't get rid of nitrate .... if it was 5000 litres with plants and deep substrate with a fish load suitable for a 650 litre tank you might have a chance.

[Ben]

Problem is aswell there is large amounts of waste water when creating pure RO water.

[kalebjarrod]

Problem is aswell there is large amounts of waste water when creating pure RO water

bingo

1/3 good water to 2/3 bad water

plus the huge pump you need to pressurize the unit

you would be better of having a trickle system and recolecting the excess water in a tank and using it for other applications like flushing toilets, watering gadens, or for less critical fish like chiclids :wink:

[Cliffeh]

I am getting 1:1 ratio from my 300gpd RO unit but point taken even then it is a lot of waste (I use mine to trickle in my pond)... if waste wasn't an issue remineralising would be. I think I would get nervous about not having control over the water in the same way I do fom my barrel.

[Merrilyn]

Wasn't Proteus using a nitrate reducer on one of the display tanks that he set up.

That was supposed to cut down on the number of waterchanges, but you still had to do some changes.

Have a look in his planted tank thread.