The gap you only see afterwards
Everybody finds fair value gaps in hindsight. On a finished chart they are obvious: three candles, a hole between the first and the third, and price coming back to it later. In the live market the same chart is full of them, old ones and new ones, half filled and long dead, and the one that matters is buried under the ones that do not.
The problem is not finding gaps. It is knowing which ones are still open.

That is the only thing the Algorex FVG Marker is strict about. It draws bullish and bearish gaps as calm zones. When price fills part of a gap, the zone shrinks to what is still open and becomes lighter. When the gap is filled completely, it disappears from the chart. What you see is what is left to trade against, nothing else.
Small noise gaps can be ignored with a minimum size measured in ATR. An optional line marks the middle of each zone, an optional alert fires when price touches an open one, and a small button hides all zones when you want the bare chart back.
Free for TradingView, MetaTrader 5 and MetaTrader 4.
