Why Aggression from Passive Fish is Dangerous

Every poker player has encountered a situation where a passive fish (a known bad poker player, amateur) sits at the table, who rarely raises, calls a lot, and prefers to check. His VPIP (Voluntarily Put Money In Pot percentage preflop) is high, and PFR (Preflop Raise percentage) is low, and it seems easy to win against him. However, these players often cause the most painful losses — when they suddenly show aggression, many do not believe their actions and make mistakes, thinking it is a bluff.

This article discusses a method using the Multiple Players tool in Hand2Note to analyze the play of passive fish. This will not only show statistics but help understand the essence of their dangerous play: when and why their sudden aggression almost always means the nuts (one of the strongest possible combinations in a hand). A step-by-step analysis will reveal the main question: why one should fear the aggression of passive fish.

Why are passive fish dangerous?

Before proceeding to the analysis, it is important to understand the main tendencies of passive fish play:

  • Fish — is usually a player with a high VPIP (45%+) and low PFR (less than 15%). The difference between VPIP and PFR is large (for example, VPIP = 55, PFR = 12).
  • Passive. Aggression from him is rare. Due to his overall passivity, when such a player suddenly starts raising, betting, or going all-in (a bet equal to the player’s entire stack), he rarely does so with a bluff or a weak hand. His range of actions narrows to strong combinations and nut draws. Typically, such a player has an Aggression Frequency (frequency of aggression) below 30 percent on each of the postflop streets.

A typical mistake when playing against a passive fish is getting used to his passivity and perceiving the table as a source of easy money. When he shows aggression, there is disbelief that such a player might have a strong hand, which often leads to losses in hands.

The goal of the analysis is to prove with data that aggression from a passive player is a red flag, ignoring which costs money.

Creating a target group of passive fish using Hand2Note

The first step is to create in Hand2Note a model of a typical “passive fish,” combining similar players into one group.

  1. To begin, open Hand2Note and go to the «Statistics» section, and in the top left corner click on «Multiple Players».
  2. In the opened window, set filters in the «BASE STATS» block:
    • Hands: Set a minimum of 500 hands. This provides a sufficient sample for analysis.
    • VPIP: Since we need fish, set VPIP from 45%.
    • VPIP-PFR: Set a minimum of 30. This automatically selects players with a large difference between VPIP and PFR, i.e., classic passive callers preflop.
  3. For the purity of the experiment in the «WINNINGS» block, you can set the filter «Win Rate EV, bb/100» less than 0. This additionally allows filtering out losing players (fish) rather than loose regulars (professional poker players who prefer a wide range of starting hands preflop).
  4. To find specifically passive players (with Aggression Frequency less than 30 percent on each of the postflop streets), you need to:
    • Below – on the right, switch the method of additional filtering by stats from Hand2Note configuration to «Textual mode».
    • Enter a formula in the input field that indicates only those players whose Aggression Frequency Flop is less than 30, Aggression Frequency Turn is less than 30, and Aggression Frequency River is less than 30.
    • Ensure the correctness of the formula by displaying a green checkmark in the lower left corner of the formula input window.
  5. Click «APPLY» to combine the statistics of all players meeting the specified criteria into one.

In this article, the formula for finding passive players was compiled based on the basic stats configuration of Hand2Note. You can create your own formula based on poker logic. More about methods for creating formulas is discussed in the articles «Multiple Players in Hand2Note» and Creating Complex Stats.

The formula for finding passive players used in the article (will work in any Hand2Note configuration that includes basic stats):

(Cases(Flop Raise or Bet) / Cases(Flop Any Action) * 100) < 30 and (Cases(Turn Raise or Bet) / Cases(Turn Any Action) * 100) < 30 and (Cases(River Raise or Bet) / Cases(River Any Action) * 100) < 30

After the calculation is completed, Hand2Note will display an active popup (in the example shown, a popup developed by the project: "Exploit HUD") with a summary of all players meeting the specified criteria, presented as a single profile.

Analysis of aggression patterns of passive fish on the postflop

If you pay attention to the «Any Bet» and «Any Raise» blocks, you can notice that passive fish very rarely make a bet on the postflop or make a raise.

The percentage of flop bet in position (the player makes a decision last on the street) for a passive fish is 32 percent, turn — 31 percent, river — 27 percent. Out of position (the player makes a decision first on the street), the passive fish bets even less: 12 percent on the flop, 20 percent on the turn, and 25 percent on the river. This means the player tends to prefer checking on the postflop rather than aggressive action — betting.

By left-clicking on any of these stats, you can study the strength of the player's hands when making actions embedded in the stat. These fillings and clarifications are built from the player's actions and the hands revealed at showdown.

Analyzing "bet-flop in position", you can notice that passive fish in this situation choose to bet mainly for strong hands and draws, almost not using bluffs with low chances of winning and ready weak hands.

Bet-flop in position

On the turn and river, the situation changes even more clearly towards strong hands when a passive fish bets:

Bet-turn in position
Bet-river in position

When making raises on the postflop, a passive fish chooses even stronger and rarer ranges of strong hands:

raise flop
raise turn
raise river

Thus, it becomes obvious: aggression from a passive player is almost always a warning light indicating a strong hand. His line of play is conservative and predictable: he waits until he is confident in his strength, and only then makes an aggressive move.

Practical conclusion and strategy change

So, the data is collected and analyzed. What to do with this information?

  1. Reconsider your calls. Next time a passive player makes a bet or raise, remember this analysis. A top pair with a weak kicker or a second pair against his range is often a loss. Folding becomes the right decision.
  2. Use aggression against a passive fish correctly. Since he rarely raises without a strong hand, you can more often apply controlled aggression. Make continuation bets on favorable boards, knowing he will fold most hands or, conversely, will try to call with unprepared hands. But it is important to be ready to give up if he suddenly shows aggression in response.
  3. Add a tag. Returning to the «Multiple Players» window, you can find real opponents from the database that fit the criteria of passive fish and mark them with a colored marker (for example, red or green). Now at the table, they can be immediately recognized and your strategy adjusted.

Conclusion: Data versus illusions

Analysis through «Multiple Players» removes the veil of mystery from the play of passive fish. What was once considered random luck or illogical action turns out to be a clear, hand strength conditioned pattern.

Their aggression is not dangerous in itself. The danger is in the unwillingness to believe it. Using Hand2Note not just for collecting statistics, but for deep studying behavior patterns helps turn losing calls against "unexpected" aggression into confident folds, which positively affects the graph.

Main conclusion: If a passive fish suddenly starts to bite, it means he already has teeth. And those teeth are a ready nut combination. It's not worth testing their strength.