Discus Filtration And Water Changes

[mrmagic2713]

hello all! i am new to the forum, and have a quick question. i would like to do a 90g tank with 6-8 small discus.  i will be using a fluval fx5, and an aqueon proflex 3 20gallon sump. the fluval will be stocked with chemipure, and seachem matrix, and the sump will be setup as a refugium. i will put hornwort, and freshwater miracle mud in the fuge (to attack nitrates) as well as more seachem matrix in the water return pump area and  possibly, a deep sandbed in the refuge as well. with that being said, how many, and how much water changes should i be doing to keep the discus happy? thaks in advance!
 

 

[Zante]

If you look in my signature you will see the current population of my discus tank.
 
I also have two amazon swords and a water lily and two pieces of wood with a healthy algae growth.
I am planning to add more plants.
 
I have COMPLETELY rescaped the tank following a house move and I had chucked out all the old sand, but I had managed to get a healthy denitrification going with an inch and a half of play sand in the display tank. I am looking to get the same conditions running again (the house move was at the beginning of April)
 
I have a mix of bioballs and ceramic rings in the back compartment of the tank (it's an AIO) plus an Eheim professional something filter (the tall one) loaded with eheim media and a 36w UV lamp (filter and lamp added only last week)
 
I have a routine of changing 100 litres every monday and my fish are happy.