Feedback Problem

[Billminpa]

Not sure if this is a bass issue or an amp issue. Last night I played a gig at a casino lounge. We were on a stage on the casino floor in front of a bar. All evening, whenever I played a "G" especially on the E string, it would start to feed back and I would immediately need to mute it. Reducing volume did not stop this. It also happened to the guitar player also.
My question is, is this due to room accoustics? Incorrect guitar/amp settings? And most importantly, is there a way to fix this when it occurs in a particular room?
Nothing I tried last night made any difference. BTW I use a P bass with flats and play through a GK Backline 600 into a Backline 410. No PA support.

[Floyd Eye]

My guess is the mics. Did you use a house PA system?

[XtheDeadPawn]

Yeah my friends and I jam on a old no name PA one of their dad owns and it feed backs when ever any of us go down a octave.

[RickenBoogie]

+1, most likely the mics and the PA. Unless you were facing your amp.

[Moe Monsarrat]

It's the EQ on the PA.