To the OP:
1. The gender of your BN may not really matter, unless you're trying to breed. If you're just concerned that two BNs of the same sex would not get along, I really don't think that's an issue. I have two males in a 60 gallon and they could care less about each other. (I do make sure that each gets their own algae wafer each morning, tho, so no food competition).
2. You said you don't have a second tank to QT? Sooner or later, then, you're going to introduce an illness to your tank and it's either going to wipe out your stock (costing money to replace) or it's going to cost money to treat. It's just not worth it. A 10 gallon tank with an HOB filter doesn't take up much room or cost much and will save you much heartache in the future. Just IME.
Good luck