Heresy

[Demosthenes]

If well planted , well filtered and fully mature is once a week change unreasonable.

If your discus are mature adults, once per week water changes is totally fine. Adults don't need the same perfect water quality and intense feeding that juveniles do. Raising the small ones to size is where you really want to just keep them in an empty box and clean everything every day.

For your plan, if your intention is to purchase young discus and grow them out, you could go ahead setting up your well balanced display tank and getting it established like you described. Just keep the discus in a separate tank and follow the best practices described on this site until they are bigger (5+ inches). I'm in the middle of doing basically the same thing.

[Filip]

Investing in a solid automatic WC system would be your best bet to keep your discus and their owner happy , without messing too much around your tank .

[Bethzb]

As someone who actually broke down my reef tank as too much work (and violence between the residents), just to replace it with a planted discus tank, I must say I find the discus much easier and even with the aggression in the tank, much calmer. That and my aggression issues may be solved by adding more fish. What I did do that you haven't mentioned is to start with 4" fish so I did not have to deal with the grow out issues. I also chose to use Stendker discus as they are quite hardy. What I now have is a 125 gallon, dirt bottom, planted tank with 8 large discus (had to cull one) and a once a week water change regime. Mind you, I am being very cautious on moving forward with adding additional fish as I know my current cleaning matches my exact bio load so..more fish would equal more waste would mean more water changes. Right now, 1 hour a week to do two tanks (I also have a 75g planted tank with angels) suites me just fine.

[bluelagoon]

If I have three in the 55 gal what is a reasonable schedule and amount to change?

Three might not last long due to aggression.You'll need at least 5-6,more if possible would be even better.Best to bye then all at once from the same source.