Hypothetical Q about Water Changes

[regal]

I have spent a lot of time and effort over the holidays to set up an auto water changing system for my discus tanks. I also have a densley stocked community tank. On the community tank I have been "experimenting" with novel techniques to reduce nitrates it has never had more than 5ppm nitrate. First it has a deep sand bed, next it has alot of pothos and peace lilies growing in a sump with strong lighting. This is called "AquaPonics" here is a link:
http://www.aquaponics.com/c_apinfo.htm

Now people are growing out a lot of fish (including cichlids) with aquaponics. My question is if there was an advance in technology to where nitrates could be kept at zero would all these water changes still be required for Discus? Is there an invisible poison released by discus unknown to science but only removed through water changes?

[Carol_Roberts]

Those invisible poisons are high counts of bacteria, fungus, viruses, disolved proteins and other organics. Many tropical fish have developed the ability to live in higher concentrations of of these pollutants. Discus have not.

Just because Bettas can live in little jars with hardly any water changes doesn't mean discus can and conversely bettas wouldn't grow better kept in schools of 6 with daily 50% water changes.

Nitrates are only one factor in the equations.

Carol :heart1:

[regal]

Ok, now lets not dismiss this question too quickly as it is
a important one. We Discus keepers (and I am an
offender too) are being pretty irresponsible by sending
1000's of gallons of water down the drain each year.
We do owe it to the environment to find a better way.

Bacteria - UV sterilizer
Fungus - ?
Virus - most of these are eliminated by removing
the bacteria
Protein - Activated Carbon
Organics - Activated Carbon

I still think nitrate is the major pollutant, if we could
find an effective means of removal it would minimize
water changes.

I disagree that nitrate is the major pollutant. From what I have heard dissolved organic material is the major reason we do water changes. We feed so much that the organic level of crap in the tank is high and can only be removed by changing the water. Nitrates have never registered in my tanks. Activated carbon is costly if used appropriately and if you get quality carbon. It also removes a lot of stuff that you don't want removed and this can lead to other problems with Discus.

I'm not dismissing the discussion of water changes. When I decided to keep Discus I did what I do in other areas of my life... I looked at people who had been successful in this field and emulated them. I read books like Wattley's Discus for the Perfectionist. I talked to local people who had kept Discus for years. I spoke to breeders that I was planning to buy fish from. The bottom line is that everyone I spoke to said that keeping large, healthy Discus was easy if you changed water often. So I started with that as a basic fact and have worked from there. I don't dismiss the possibility that there may be another way of succeeding but I doubt you'll find a cheaper, easier way to do it. But if you do, please tell us so we can all try it.

Dave

[regal]

Look at the pictures of the discus in South America, thier natural habitat is littered with decaying organic matter (leaves and twigs). It would be interesting to find out what trees or shrubs those are that are growing in that acid water. It is possible that the natural resistance to organic compounds was accidentally bred out of discus over the years of keeping them in sterile tanks. I'm a ChE and just can't accept the water change dogma without asking why and finding a better way.

[Ralph]

It seems to me that if there is something in our tanks that is unhealthy for discus that there should be some way to remove that substance besides major water changes. But without knowing specifically what that substance is, it is difficult to come up with something to remove it. But it is only because people keep asking the question that this situation will change. It's similar to the prefilter days, before people understood the ammonia-nitrifying bacteria thing, I'm sure there were people then wondering why they couldn't keep more than two goldfish in their tank and how they could change that.
The problem is that major research is only done by companies hoping to turn it into a profit (or colleges hoping to get grants from companies that will turn it into a profit). And there is not that much money in discus. If a solution is to be found, it will most likely happen in someones basement, stumbled upon by somebody asking the same questions that you are.
But I understand the frustration of long time discus keepers, they know what works and are invested in the WC method. That's not a bad thing, these same people have helped me keep my fish alive and healthy.
As to the list of likely toxins in a discus aquarium, it includes all those that Carol and Dave mentioned and probably some others (and there is the possibility that it is caused by a combination of several of the substances).
My advise: keep asking the questions, it may happen in your basement (if you have one that is).