diff --git a/CMakeLists.txt b/CMakeLists.txt
index fbb04a5..9e4619c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3,5 +3,5 @@ project(aoc_2021 C)
 
 set(CMAKE_C_STANDARD 99)
 
-add_executable(aoc_2021 src/main.c src/day_1.c src/day.h src/day_2.c src/puzzle_input.c src/puzzle_input.h src/day_3.c src/day_4.c src/day_5.c)
+add_executable(aoc_2021 src/main.c src/day_1.c src/day.h src/day_2.c src/puzzle_input.c src/puzzle_input.h src/day_3.c src/day_4.c src/day_5.c src/day_6.c)
 target_link_libraries(aoc_2021 m)
diff --git a/inputs/day_6.txt b/inputs/day_6.txt
new file mode 100644
index 0000000..57e0ce5
--- /dev/null
+++ b/inputs/day_6.txt
@@ -0,0 +1 @@
+4,1,3,2,4,3,1,4,4,1,1,1,5,2,4,4,2,1,2,3,4,1,2,4,3,4,5,1,1,3,1,2,1,4,1,1,3,4,1,2,5,1,4,2,2,1,1,1,3,1,5,3,1,2,1,1,1,1,4,1,1,1,2,2,1,3,1,3,1,3,4,5,1,2,2,1,1,1,4,1,5,1,3,1,3,4,1,3,2,3,4,4,4,3,4,5,1,3,1,3,5,1,1,1,1,1,2,4,1,2,1,1,1,5,1,1,2,1,3,1,4,2,3,4,4,3,1,1,3,5,3,1,1,5,2,4,1,1,3,5,1,4,3,1,1,4,2,1,1,1,1,1,1,3,1,1,1,1,1,4,5,1,2,5,3,1,1,3,1,1,1,1,5,1,2,5,1,1,1,1,1,1,3,5,1,3,2,1,1,1,1,1,1,1,4,5,1,1,3,1,5,1,1,1,1,3,3,1,1,1,4,4,1,1,4,1,2,1,4,4,1,1,3,4,3,5,4,1,1,4,1,3,1,1,5,5,1,2,1,2,1,2,3,1,1,3,1,1,2,1,1,3,4,3,1,1,3,3,5,1,2,1,4,1,1,2,1,3,1,1,1,1,1,1,1,4,5,5,1,1,1,4,1,1,1,2,1,2,1,3,1,3,1,1,1,1,1,1,1,5
\ No newline at end of file
diff --git a/src/day.h b/src/day.h
index 7be662a..f14f014 100644
--- a/src/day.h
+++ b/src/day.h
@@ -6,5 +6,6 @@ int day_2();
 int day_3();
 int day_4();
 int day_5();
+int day_6();
 
 #endif //AOC_2021_DAY_H
diff --git a/src/day_6.c b/src/day_6.c
new file mode 100644
index 0000000..18e746c
--- /dev/null
+++ b/src/day_6.c
@@ -0,0 +1,83 @@
+#include <stdio.h>
+#include <stdint.h>
+
+#include "puzzle_input.h"
+#include "day.h"
+
+#define STATES_MAX_LEN 500
+#define FISH_DAYS 9
+
+uint8_t states_g[STATES_MAX_LEN];
+
+
+typedef struct {
+    uint64_t spawn_count[FISH_DAYS];
+    uint8_t day_ndx;
+} fish_buffer_t;
+
+void insert_fish_at_ndx(fish_buffer_t * buff, uint8_t day_ndx, uint64_t count) {
+    uint8_t norm_ndx = (buff->day_ndx + day_ndx) % FISH_DAYS;
+    buff->spawn_count[norm_ndx] += count;
+}
+
+uint64_t fish_today(fish_buffer_t * buff) {
+    return buff->spawn_count[buff->day_ndx];
+}
+
+void inc_day(fish_buffer_t * buff) {
+    buff->day_ndx = (buff->day_ndx + 1) % FISH_DAYS;
+}
+
+parse_ret_t parse_byte_from_buffer(char * buffer, void * data, uint16_t index) {
+    uint8_t * initial_states = (uint8_t *)data;
+    int64_t val;
+    parse_ret_t res;
+
+    res = parse_long(buffer, &val, 10);
+
+    if (res != PARSER_OK) {
+        return res;
+    }
+
+    initial_states[index] = (uint8_t)val;
+
+    return PARSER_OK;
+}
+
+int day_6() {
+    parse_ret_t res;
+    uint16_t len;
+    uint16_t day = 0;
+    uint64_t fish_count;
+    fish_buffer_t fish_buffer = {0};
+
+    res = read_input_split_on("../inputs/day_6.txt", (void *)states_g, 500, parse_byte_from_buffer, &len, ',');
+
+    if (res != PARSER_OK) {
+        printf("Unable to parse input data: %d", res);
+        return -1;
+    }
+
+    for (int initial_ndx = 0; initial_ndx < len; initial_ndx++) {
+        fish_buffer.spawn_count[states_g[initial_ndx]]++;
+    }
+
+    fish_count = len;
+
+    while (day < 256) {
+        uint64_t spawns_today = fish_today(&fish_buffer);
+        inc_day(&fish_buffer);
+        insert_fish_at_ndx(&fish_buffer, 6, spawns_today);
+
+        fish_count += spawns_today;
+
+        day++;
+
+        if (day == 80) {
+            printf("PART 1: Fish count: %lu\n", fish_count);
+        }
+    }
+
+    printf("PART 2: Fish count: %lu\n", fish_count);
+    return 0;
+}
diff --git a/src/main.c b/src/main.c
index ab43528..7f54e60 100644
--- a/src/main.c
+++ b/src/main.c
@@ -31,6 +31,9 @@ int main(int argc, char * argv[]) {
         case 5:
             day_5();
             break;
+        case 6:
+            day_6();
+            break;
         default:
             printf("Invalid day ding dong!\n");
             return -2;
diff --git a/src/puzzle_input.c b/src/puzzle_input.c
index 2c16cf7..4cf43e7 100644
--- a/src/puzzle_input.c
+++ b/src/puzzle_input.c
@@ -46,7 +46,7 @@ parse_ret_t parse_long_base_2_from_buff(char * buffer, void * data, uint16_t ind
     return parse_long_base_from_buff(buffer, data, index, 2);
 }
 
-parse_ret_t read_input_single_line(const char * file_path, void * data, uint16_t max_len, input_parser_t parser, uint16_t * len) {
+parse_ret_t read_input_split_on(const char * file_path, void * data, uint16_t max_len, input_parser_t parser, uint16_t * len, char sep) {
     char buffer[BUFFER_SIZE];
     int c;
     int ret = 0;
@@ -56,7 +56,7 @@ parse_ret_t read_input_single_line(const char * file_path, void * data, uint16_t
     if (file != NULL) {
         int buffer_ndx = 0;
         while ((c = fgetc(file)) != EOF) {
-            if (c == '\n') {
+            if (c == sep) {
                 buffer[buffer_ndx] = 0;
 
                 ret = parser(buffer, data, data_ndx);
@@ -177,3 +177,7 @@ parse_ret_t read_input_multi_line(const char * file_path, void * data, uint16_t
 
     return ret;
 }
+
+parse_ret_t read_input_single_line(const char * file_path, void * data, uint16_t max_len, input_parser_t parser, uint16_t * len) {
+    read_input_split_on(file_path, data, max_len, parser, len, '\n');
+}
diff --git a/src/puzzle_input.h b/src/puzzle_input.h
index 52466f5..60a18bd 100644
--- a/src/puzzle_input.h
+++ b/src/puzzle_input.h
@@ -14,6 +14,7 @@ typedef enum {
 typedef parse_ret_t (*input_parser_t)(char * buffer, void * data, uint16_t index);
 
 parse_ret_t read_input_single_line(const char * file_path, void * data, uint16_t max_len, input_parser_t parser, uint16_t * len);
+parse_ret_t read_input_split_on(const char * file_path, void * data, uint16_t max_len, input_parser_t parser, uint16_t * len, char split);
 parse_ret_t read_input_multi_line(const char * file_path, void * data, uint16_t max_len, char * sep, input_parser_t parser, uint16_t * len);
 
 // Parsers