Min. IB Account Size to Keep Account Open?

What is the min amount you have to keep in your IB Reg T Margin account to keep it open?

 

I kept it open for a few months a while back with about 1500 usd in it, just to get quotes etc. Don't know what the minimums are.

 

The minimum is 0. The only 2 side effects of a low netliq are (i) higher monthly activity fee ($20) below $2000 and (ii) market data is automatically turned of below $500.