At what point is volume too low to trade?

for scalping, daytrading what % is too low to trade? < than average? 5% > than average? Trading GU. 5m.

Not sure what you exactly mean by ~5%...

But volume in forex isn't quite as transparent as most markets. You won't see true market volume since the market isn't centralized.

Instead, most brokers use "tick" volume, which only measures the amount of 'ticks' within a give time period. The theory is, with more activity in the market, the more ticks, and the more 'volume'. However, in illiquid moments, tick volume can spike when smaller trades can push the market around more frequently...so this method is quite flawed.

What times of day do you trade?

What you really want to focus on is liquidity, which is how large the size is on either side of the spread as provided by liquidity providers. . . the "market" link at the top from ForexFactory has a measure for this.