regarding as to whether they will get on or not. I hold several small and large plecs in a tank with a bgk fish and never had a problem.
With regards to your tank though, it is far too small to hold a bgk fish. Although others will have differing experiences and opinions I can say that my bgk fish grew from a 3" fish into a 12" fish in 12 months and it's still growing, although it has slowed down somewhat.