How Many Odessa Barbs In 125G

[Brahmza]

Hey everyone. Going to be bringing back my severums in the next few days (species was labeled incorrect), and I'm looking to replace them with something more active, and something I could have in larger numbers. My tank stocking, without the severums, looks like this
1 Pair of Blue Acara
7 Goldiei Rainbows
5 Geo Red Heads
4 Synodontis Petricola
1 Mango Pleco
If I were to add Odessa Barbs, how many would I be able to add? I'm unsure as to where my current stocking level is at...this is my first tank over 55 gallons!

Feel free to mention any other fish come to mind that might fit the bill.
(Also playing with the idea of adding a group of Turquoise Rainbows..)

Edit: Tank dimensions are 72x18x23, PH of 7.1, ~900GPH flowrate

 

[BerryAttack]

i would say with the stocking you have right now you are find. the pleco will get around 11 inches.. so if you think it'll ever get to large i'd switch it out for a bristle nose pleco.. just so te bio load is smaller etc etc.
if you are keeping your maintenance up each week then i see you having no issue getting more fish.
the geo redheads will most likely spawn so you might have issues with that and the blue acara.
there might be aggression between the cichlids and rainbows you have... so watch that.
the synodontis petricola, like all catfish will eat anything that fits in it's mouth.. so getting schooling fish you'll have to make sure it's large enough not to fit in a 5 inch fish's mouth... keeping that in mind you'll need something large enough. the obessa barbs seem good, they school fast and should become large enough to not have to worry about being food.

 

[Brahmza]

The synodontis petricola's at max size get to be right around 4" only, so I don't believe I'll have an issue with them eating my fish .
That's awesome to hear! As far as maintenance goes, I'm running two canisters each rated for 265G, and each have a flow-rate of 450GPH. I'm doing 20% water changes weekly.
I have my tank arranged to encourage the cichlids to stay separate. On the right side I have a lot of plants with a few caves, and very minimal open substrate, which Is where the Acara's like to hang out, and on the left it's more open-substrate with driftwood caves where the Geo's spend most of their time. Though I'm sure I'm going to encounter some aggression issues, hopefully I'll be able to handle it.
How many Odessa barbs would you suggest? Or how many Odessa barbs would put my tank at a full-stocking level?