good morning Kamakasi
I have had GBRs in my tank before. I find that they pretty much like to hang out at the bottom of the tank as does your two BNs and the two loaches as well.
IMO I think that the bottom portion of your 29g tank is pretty much filled now.
The GBRs get along pretty much with others but I have never had loaches or BNs so I really couldnt tell you if they would get along well with the GBRs.
I love GBRs and can see why you would want to add them.. they are great looking fish for sure.
