Why are such large/frequent water changes needed?

[speakerguy]

Is it just for nitrate and detritus removal, or is there another reason or reasons? What's the chemistry behind the large and frequent water changes people do?

[rwel4809]

it's because Discus come from such low nutrient water that is constantly replaced through frequent rainfall. they do not like too much nitrate (N03) and cannot tolerate amonia (N01) or nitrite (N02).

The amount of water changes you do depends on your water chemistry to some extent - as long as you keep your N01+N02 at 0 and your N03 < 10 ppm then you are alright.

The amount of water changes therefore depends on how heavily your tank is stocked, how heavily you feed, and whether you have enough plants to suck up the excess nutrients.

Some people with densly planted tanks who feed lightly get away with 30% waterchange per week. Most of us do more though.

HTH

Robert

[Hollowman]

I think it comes down to keeping the fish in the best conditions that we possibly can. We all know that they thrive in clean, stable conditions with a healthy and varied diet, so the large, regular water changes is the way we do it.
I think of it as living with a heavy smoker in one room with no doors or windows. How long will it take before you stink of smoke and have to re-breath the fumes. Fish in a tank are the same, as we change the water it is like flushing the toilet and replenishing a healthy enviromnent.
The fish also suffer from the effects of DOC's (Disolved Organic Compounds) which the filters cannot reduce, the DOC's increase as the time between water changes increases. DOC's come from the fish, food and bacteria, but it is very hard to measure, but the effects are seen in things like the stunting of fish.
I think at the end of the day reducing the pollution within the tank will pay dividends. We rely on biological filtration to convert fish waste to non-toxic substances and mechanical filtration to physically remove waste, this can be just a simple vacuum or a sponge over the intake to your external filter, it all helps, but the changing of large volumes of water is the best way to achieve the best conditions.
I do large water changes because it makes my fish happy and feel better, this is clearly noticable, when they are happy i am happy.

jmo

Hollowman

[tomahawk]

It is because Discus comes from that part of the world and waterbody, which offers one of the cleanest source of natural water. When we keep them in an aquarium, we try our hardest to maintain the same hydrosphere. Frequent water change is thus most important.

[FNQ]

Don't have to be large if they are frequent. If you removed changed 10cm of water every day you could replace it straight out of the tap. The temperature changes are minimal and any chlorine etc. is diluted to such an extent that it has no impact and is dissipated within 24 hours.

[rwel4809]

Don't have to be large if they are frequent. If you removed changed 10cm of water every day you could replace it straight out of the tap. The temperature changes are minimal and any chlorine etc. is diluted to such an extent that it has no impact and is dissipated within 24 hours.

Sorry, but I don't think that this is very good advice.

:?

10 cm would be 15 to 20 % of the water in most people's tanks.

I wouldn't risk it myself, you never know how much chlorine or chloromine there is in tap water. For example, in sydney, when there is heavy rain the water company up the chloromine to stop algea bloom...


Robert