I cannot add any new residents that will grow larger in
size.
I did want another type of loach... it looks like an eel... but
was advised against it cause if the shrimps bred, the loach will
eat them all up! 
BTW, Pinky, the gobies are soooo amusing! They like to act
aggressive but their action is so slow! 
Erhmm if the shrimps bred, your gobis will eat them all up
anyway.
What's the difference???
Oh the Hillstream loach don't get very big. Max length is around
3 inches + They are scavangers and very peaceful fishes
The eel-like loach is the Kuhli Loach. It should fit well in
your tank too I think coz those are scavangers too
And yes brine shrimp are at the bottom of the food chain
>.<
Everything I know eat brine shrimps >.<