How Many Malawi In A 55G?

[paradiddle]

How many Malawi can I stock in a heavily filtered 55G
Filtration is a fluval fx6 (3500L/hr) with matrix, bioballs, biomax, carbon, fine filter wool x6, 1 carbon filter pad, 2 large sponges.
+ a fluval 305 with biomax nodes in 3 trays, fine sponge and carbon.

I already have 9 cichlids and the tank is heavily rocked but looks empty fish wise.
Largest fish 3 inches, smallest fish 1inch

Any help? Want to order some fish online but need to know how many I can order.

 

[BrianMcC]

it really depends what species you have already, I have my tanks overcrowded but now I have had to buy a 500L as they have grown, filter wise its a great filter so shouldn't have much problem there but lots and lots of water changes on an overstocked tank are required.
You have stated the largest fish is 3 inches and smallest is one is that them fully grown?