Sending an email each time a condition is met from a Spreadsheet in Apps script

I'm trying to write some code in Apps Script that triggers an email each time a condition is fulfilled in a Spreadsheet.

This spreadsheet contains the age of different transgenic lines of fish (the ages of the fish are automatically updated in the spreadsheet) and each of these transgenic lines has an associated caretaker with an email address. My idea is to trigger an automatic email using Apps script that is sent to the assigned caretaker each time one of these transgenic lines becomes older than 2 years old. However, I haven't been able to make it work yet. I'm not really sure which part of my code is preventing it from working properly.

Below I attach an example of how the spreadsheet would look like, as well as an example of the code that I've been trying to use (I'm a beginner when it comes to coding, so it's possible that there are many basic errors in it):

Spreadsheet example

function fishalert() {
  var subject = 'Fish aging alert';
  var years = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Sheet1").getRange("C2:C10").getValues();
  if (years > 2){
    for(r=2;r<20;r++){
      var name = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Sheet1").getRange(r,1).getValue();
      var emailaddress = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Sheet1").getRange(r,4).getValue();
      var message = 'Line ' + name + ' is more than 2 years old';
      MailApp.sendEmail(emailaddress, subject, message);
    }
  }
}