return function(feesh, dt, food, headerbuttons, money)
  for fi, n in ipairs(feesh) do
    bench.startBenchmark('update_fish_eases')
    for _, e in ipairs(n.eases) do
      e.a = e.a + dt * e.speed
    end
    for i, e in ipairs(n.eases) do
      if e.a > 1 then
        local sumx = 0
        local sumy = 0
        for i2, e2 in ipairs(n.eases) do
          if i ~= i2 then
            sumx = sumx + mix(e2.fromx, e2.x, FISH_EASE(math.min(e2.a, 1)))
            sumy = sumy + mix(e2.fromy, e2.y, FISH_EASE(math.min(e2.a, 1)))
          end
        end

        sumx = sumx + e.x
        sumy = sumy + e.y

        n.x = sumx / #n.eases
        n.y = sumy / #n.eases
        e.fromx = e.x
        e.fromy = e.y

        e.a = e.a - 1
        
        local angle = math.random(-FISH_ANGLE, FISH_ANGLE)
        local str = math.random(70, 200)/200/4
        angle = mix(angle, math.deg(math.atan2((0.5 + math.sin(love.timer.getTime()/10 + fi) * 0.2) - n.y, 0)), 0.1) -- slightly head towards the middle, to prevent getting stuck at the bottom or top

        local followingObj = (n.shortestfood and food[n.shortestfood] and n.size ~= 4) or (n.shortestfood and feesh[n.shortestfood] and n.size == 4)
        if n.eattimer <= 0 and not n.dead then -- needs to follow something
          local mx, my
          if n.eattimer <= 0 then
            if n.size == 4 then -- carnivore
              if n.shortestfood and feesh[n.shortestfood] then
                local f = feesh[n.shortestfood]
                mx, my = f.x, f.y
              elseif frame % FISH_FOOD_CHECK_FREQ == 0 then
                local minfood = 0
                local mindist = 9e9

                for i,f in ipairs(feesh) do
                  if f.size == 0 then
                    local dist = math.sqrt(math.pow(math.abs(f.render.x - n.render.x), 2) + math.pow(math.abs(f.render.y - n.render.y), 2))
                    if dist < mindist then
                      mindist = dist
                      minfood = i
                    end
                  end
                end

                if minfood ~= 0 then
                  n.shortestfood = minfood
                end
              end
            else
              if n.shortestfood and food[n.shortestfood] then
                local f = food[n.shortestfood]
                mx, my = f.x, f.y
              elseif frame % FISH_FOOD_CHECK_FREQ == 0 then
                local minfood = 0
                local mindist = 9e9

                for i,f in ipairs(food) do
                  local dist = math.sqrt(math.pow(math.abs(f.x - n.render.x), 2) + math.pow(math.abs(f.y - n.render.y), 2))
                  if dist < mindist then
                    mindist = dist
                    minfood = i
                  end
                end

                if minfood ~= 0 then
                  n.shortestfood = minfood
                end
              end
            end
          end
          if mx and my then
            angle = math.deg(math.atan2(my - n.y, mx - n.x)) + math.random(-FISH_FOLLOW_RANDOM, FISH_FOLLOW_RANDOM)
            str = math.random(70, 200)/200/8
          end
        end

        local x = math.cos(math.rad(angle)) * str
        local y = math.sin(math.rad(angle)) * str

        if not (followingObj or n.dead) then
          x = x * math.sign(n.render.x - n.render.prevx)
        end

        e.x = n.x + x
        e.y = n.y + y

        e.x = 1 - math.abs(e.x%2-1)
        e.y = 1 - math.abs(e.y%2-1)

        local fheight = (HEADER_HEIGHT * love.graphics.getWidth()/640)/love.graphics.getHeight()
        if e.y < fheight then
          e.y = e.y + (fheight - e.y) * 2
        end

        e.speed = 1 / (math.sqrt(math.pow(math.abs(e.x - e.fromx), 2) + math.pow(math.abs(e.y - e.fromy), 2))/2) / 15
        if n.eattimer < FISH_FOOD_HUNGRY or followingObj then
          e.speed = e.speed * 1.3
          if n.size == 4 then e.speed = e.speed * 1.1 end
        end
        if n.dead then
          e.speed = e.speed * 0.2
        end
      end
    end
    bench.stopBenchmark('update_fish_eases')

    bench.startBenchmark('update_fish_position')
    n.x = clamp(n.x, 0, 1)
    n.y = clamp(n.y, 0, 0.5)

    n.lifetime = n.lifetime + dt
    n.eattimer = n.eattimer - dt
    n.moneytimer = n.moneytimer - dt

    if n.moneytimer < 0 and not n.dead then
      n.moneytimer = n.moneytimer + math.random() * 5 + 5

      if n.size > 0 then
        local type = 2
        if n.size == 1 then type = 1 end
        if n.size == 3 then type = 3 end
        if n.size == 4 then type = 4 end
        if n.star then type = 3 end
        table.insert(money, constr.money(n.render.x, n.render.y, type))
      end
    end

    local sumx = 0
    local sumy = 0
    for _, e2 in ipairs(n.eases) do
      sumx = sumx + mix(e2.fromx, e2.x, FISH_EASE(e2.a))
      sumy = sumy + mix(e2.fromy, e2.y, FISH_EASE(e2.a))
    end

    n.render.prevx = n.render.x
    n.render.prevy = n.render.y
    n.render.x = sumx / #n.eases
    n.render.y = sumy / #n.eases

    n.render.x = clamp(n.render.x, 0.05, 0.95)
    n.render.y = clamp(n.render.y, 0.1, 0.85)
    bench.stopBenchmark('update_fish_position')

    bench.startBenchmark('update_fish_colission')
    if n.size == 4 then
      if n.shortestfood and feesh[n.shortestfood] and frame % FISH_COLISSION_CHECK_FREQ == 0 and not n.dead then
        local f = feesh[n.shortestfood]
        local dist = math.abs(n.render.x - f.render.x) + math.abs(n.render.y - f.render.y)

        if dist < FOOD_HITBOX then
          playSound('chomp', 1, 1 + math.random() * 0.1 - 0.05)
          table.remove(feesh, n.shortestfood)

          n.eattimer = FISH_FOOD_3_COOLDOWN
          n.render.eattimer = 0
          n.shortestfood = -1
        end
      end
    else
      if n.shortestfood and food[n.shortestfood] and frame % FISH_COLISSION_CHECK_FREQ == 0 and not n.dead then
        local f = food[n.shortestfood]
        local dist = math.abs(n.render.x - f.x) + math.abs(n.render.y - f.y)

        if dist < FOOD_HITBOX then 
          playSound('slurp', 1, 1 + math.random() * 0.1 - 0.05)
          table.remove(food, n.shortestfood)
          local cooldowns = {FISH_FOOD_1_COOLDOWN, FISH_FOOD_2_COOLDOWN, FISH_FOOD_3_COOLDOWN}

          n.eattimer = cooldowns[f.type] or FISH_FOOD_3_COOLDOWN
          n.render.eattimer = 0
          n.shortestfood = -1

          if f.type == 4 then -- star potion
            if n.size == 2 or n.size == 3 then
              n.star = true
            else
              n.eattimer = FISH_FOOD_DEAD
              playSound('explode')
            end
          else
            if n.lifetime > FISH_AGE_MEDIUM and n.size == 0 then
              n.size = 1
              playSound('grow')

              if not headerbuttons[1].open and not headerbuttons[1].closed then
                headerbuttons[1].open = true
                headerbuttons[1].openanim = 0
              end
            end
            if n.lifetime > FISH_AGE_BIG and n.size == 1 then
              n.size = 2
              playSound('grow')

              if not headerbuttons[2].open and not headerbuttons[2].closed then
                headerbuttons[2].open = true
                headerbuttons[2].openanim = 0
              end
              if not headerbuttons[3].open and not headerbuttons[3].closed then
                headerbuttons[3].open = true
                headerbuttons[3].openanim = 0
              end
              if not headerbuttons[4].open and not headerbuttons[4].closed then
                headerbuttons[4].open = true
                headerbuttons[4].openanim = 0
              end
            end
            if n.lifetime > FISH_AGE_KING and n.size == 2 then
              n.size = 3
              playSound('grow')
            end
          end
        end
      end
    end
    bench.stopBenchmark('update_fish_colission')

    bench.startBenchmark('update_fish_render')
    if frame % FISH_RENDER_FREQ == 0 then
      local dt = dt * FISH_RENDER_FREQ

      local iter = FISH_RENDER_ITERS
      local iteroff = FISH_RENDER_ITEROFF
      local xspeed = {}
      local yspeed = {}
      local angle = {}

      local sumxiter = {}
      local sumyiter = {}
      for i = 1, iter do
        local off = i * iteroff

        local sumx2 = 0
        local sumy2 = 0
        for _, e2 in ipairs(n.eases) do
          sumx2 = sumx2 + mix(e2.fromx, e2.x, FISH_EASE(e2.a + off))
          sumy2 = sumy2 + mix(e2.fromy, e2.y, FISH_EASE(e2.a + off))
        end
        table.insert(xspeed, (sumx2 - (sumxiter[i - 1] or sumx)) / #n.eases)
        table.insert(yspeed, (sumy2 - (sumyiter[i - 1] or sumy)) / #n.eases)
        table.insert(angle, math.atan2(sumy2 - (sumyiter[i - 1] or sumy), sumx2 - (sumxiter[i - 1] or sumx)))

        table.insert(sumxiter, sumx2)
        table.insert(sumyiter, sumy2)
      end

      n.render.xspeed = sum(xspeed)
      n.render.yspeed = sum(yspeed)
      n.render.angle = sum(angle)
    end

    n.render.turn = n.render.turn + dt * math.sign(n.render.x - n.render.prevx) * 2
    n.render.turn = clamp(n.render.turn, 0, 1)
    if n.render.turn == 0 or n.render.turn == 1 then
      n.render.swim = (n.render.swim + dt * (math.abs(n.render.xspeed) * 250 + 0.5)) % 1
    else
      n.render.swim = 0
    end

    n.render.eattimer = n.render.eattimer + dt * 3
    if n.render.eattimer < 1 then
      n.render.swim = 0
    end

    if not n.dead then
      n.render.turndir = math.sign(n.render.x - n.render.prevx)
    end

    local m = n.eattimer < FISH_FOOD_HUNGRY and 1 or -1
    n.render.hungry = clamp(n.render.hungry + dt * m * 3, 0, 1)
    bench.stopBenchmark('update_fish_render')

    if n.eattimer <= FISH_FOOD_DEAD and not n.dead then
      playSound('die')
    end
    if n.eattimer <= FISH_FOOD_DEAD then
      n.dead = true

      local timeSinceDead = math.abs(n.eattimer - FISH_FOOD_DEAD)
      n.render.y = n.render.y + timeSinceDead/5 * math.min(timeSinceDead, 1)
      n.render.y = clamp(n.render.y, 0, 0.85)
      if n.render.y == 0.85 then
        n.render.deathanim = n.render.deathanim + dt
        if n.render.deathanim > 1 then
          table.remove(feesh, fi)
        end
      end
    end
  end
end