I'm relatively new to the Discus scene but not so much to the science thing. I've been scouring the internet for reputable Discus experiments (there aren't many) and journal articles.

So maybe this is a tired debate/discussion, but are there any supporting facts to massive water changes? So far all I've found is anecdotal evidence.

I have found articles about fat/protein diets. I haven't really sat down with it to really dissect the conclusions but it seems to match up with the advice given here.

The rules for raising discus are numerous. One breeder I spoke with said he doesn't ever change his water but once a week and he gets great results.

http://discusguide.com/massive-discus-growth/

Basically, from the link above, Jack Wattley had two tanks with two different schedules for water changes.

Possible problems.
1) Two different sized tanks. Maybe it's not the water changes but it was easier for the fish to find food. Maybe they were less stressed since they knew the boundaries of the tank and knew there weren't any threats. A smaller tank is more susceptible to temperature fluctuations. I would say the latter might be a downfall for small tanks but maybe it's healthy for fish (can we make such an assumption?).
2) Limited experiment. I don't know how many fish were in each tank, but the fewer the samples the higher the probability that one tank got 'better' stock than the other.
3) It also lacks some other data. Like how many discus survived. I'm not saying that Wattley hid facts (rather common in science journals), but what if he had 20 fish in each tank and 10 died in the smaller tank and all lived in the larger tank. The 10 that lived were stronger specimens, that's why they survived. So on average, their size was greater than with the other tank.
4) The article above is secondhand story, but also, how tightly controlled were the other parameters (i.e. maybe one tank had different temps, different amounts of light, the larger tank was set next to heavy foot traffic, etc).

I'm not saying that Wattley (or anyone else giving the advice) is wrong or lying. I'm just curious how much concrete evidence is there.

A more controlled study would also find what the optimal water change schedule is... for instance, a study in Malaysia found that the more protein you gave the discus the faster they grew (we know this...) but the researcher also found that too much and the discus didn't grow as fast. Could there be a point that there are too many water changes (i.e. effects of stressed out fish).