How many Discus in one tank

Well I finally got my pair of full grown discus out of my 20 gallon and into the new 58 gallon tank. All is doing well. Some algae but not much. Most of the algae is green algae on anubius leaves. Does this mean I need more phosphates.?

Anyway, the (2) discus have been in the tank for about 4 weeks. The male is keeping the female in a small corner of the tank. Won't let her out. Not even for food. Beats on her pretty good. It seems he likes the tank swims everywhere. Has explored every corner of the tank.

I wanted to purchase another 1-2 discus to try and calm him down a bit so the other female can come out to eat and swim around. The question is, is the tank large enough to house another 1-2 discus?

The tank is a 36"x18"x20" (58 gallon). There are about 14 tetras in the tank as well. In addition to (3) cory's and a bunch of algae eating shrimp. How many can I safely put into this tank without overdoing the bioload and causing algae to creep up?

 

They are Sterbai cory's. I have had them for 4 years. I run the tank temps in the 82-84 range.

I was thinking of adding two but was even unsure if the tank could support two. I am worried about the nitrate getting too high causing algae.

 

Oh cool, you speak from experience. You have a 60 gallon with how many discus? 7? I am running an Eheim Pro and an Eheim 2215. (use a co2 reactor inline).

In terms of nitrates, I wasn't sure of how many the tank could hold. I used to have the (2) discus in a 20gallon tank and I added no nitrates. All the nitrates came from the fish. I still had to do 50% water changes 3 times a week to keep the nitrates in a manageable area.

Do you think adding more discus will help the (2) discus I currently have get along better? They are actually a pair and have laid eggs once. I guess they only get along when both are willing to breed.