Problem I have seen is that the Geo can get a little aggressive and take over the tank if they are breeding or if one male is showing he is top dog, I just got some from a Guy that was having that issue, the discus were crammed into a corner as the Geo was showing he was top fish.
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You can keep discus with smaller, more peaceful geos in a large tank. Try things like G. parnaibae or G. Tapajos orange heads. By "pearl geo" I'm assuming you mean G. brasiliensis? If so, that's too large and aggressive for a discus setup.