One thing to consider is that almost every discus with the exception of wild caught was born and raised in the conditions that you are talking about, meaning they have never known anything else. have you ever kept discus? I see rather large and very healthy discus all the time from breeders that stay in the 82 to 84 degree mark, I have been keeping mine at 84 for a few years now with no problems, and a mess load of plants, look at my tank in introductions and greetings, its titled "hello from Wi." the other thing that really makes a difference in the overall health of discus is there diet hands down, a lot of the things that they eat in the river where they come from are just not reasonable for a aquarium, and again they were born and raised without it. As for the higher motabolism, discus are very suceptable to flagletts, the higher temp. and increased motabolism, decreases the risk of this diseases (is a fish really happy when he has flagletts). Yes flagletts are easily treatable but who in the hell wants to try to cath discus out of a heavily planted tank, my tank is 125 gal and I would rather stick a knife in my eye then try to catch them to quarintine them. If you buy a fish from a breeder that is not a juvenile the chances are it may be a year old or more, meaning they have been in that water temp there whole life, if you bring them home and put them in a 10 degree difference from the past year or more of there life I dont think they would be very happy. I think I will stick to the higher temperatures rather than chance flushing about 450 dollars worth of my fish down the drain do to chance of disease at lower temps.
I agree with almost everything you say! I would not want to put $450 dollars worth of fish in peril. But while your expensive fish are in quarantine, why not treat them preventatively for the flagellates with Paragone (or something else with Metrondiazole or sim) and then very slowly acclimatise them to their natural temperatures monitoring carefully?
Obviously a 10 degree temperature drop would cause the fish immense stress if performed quickly and they would probably promptly catch whitespot (amongst other things) if this happened. There is quite a bit of research done on the effects of temperature change in fish and how slow acclimatisation is needed, especially when lowering temperatures.
I totally agree with your comments about captive bred discus having been kept at those high temperatures all their lives, but many breeders always keep their fish in bare tanks and in quite hard water too. Do you keep all your discus in the same conditions in these respects? After all bare tanks done partly to minimise waste and any possibility of diseases. Hard water is used by some because it improves the growth rate apparently. But if these fish were growing at the normal temperatures would this be an issue?
You can change these parameters, why not the temperature too?
I never said the discus wouldn't grow large and be apparently healthy in unnatural conditions and have seen many in tanks too. The breeders/dealers I have talked to though have never been able to pin down exactly why they use these high temperatures, apart from it keeps certain diseases at bay. I don't think they wanted to abmit that a part of the reason was that their fish grew more rapidly and hence reached a saleable size quicker.
As the main cause of disease is normally stress don't you think we should be doing all we can to reduce this in our pets? These fish evolved for millions of years living at their natural temperature range, which included the ability to tolerate periods of high temperature. Why not take that as a good basis over 40ish years of captive breeding?
I have kept discus but they really didn't have enough room as they grew. They were kept at normal temperatures (26oC) in soft water with plants and other fish and were in absolutely bullish health. They were 'bog standard' Blue discus. I wouldn't keep any more until I have a bigger tank and would get some wilds, or near wild, preferably Tefe greens (but will need to wait for a long while to get the funds necessary). I currently do keep wild angels though.
I hope you don't think I was trying to have a go at anyone or the way anyone else does things. I can, I'm afraid, come across far more bluntly than I usually mean to. If something works for you then great, but they really don't NEED these high temperatures. If they did, why wouldn't the angelfish, tetras, catfish etc. that live alongside them in the wild need them too?
