Chill Penguin's Stage:
When you reach the cave with the Mech, use the Mech to jump on to the ceiling of the cave. Use Fire Wave (Flame Mammoth's weapon) on the igloos to destroy them and you should pick the heart container up.

Boomer Kuwanger's Stage:
You'll be able to easily see the tank when you get to it. Just use the Boomerang to get it.

Sting Chameleon's Stage:
Instead of climing up the wall before the cave where rocks fall to fight the mech that gives you the body armor upgrade drop in the hole and destroy the blocks on the platform near the bottom, then dashjump to the right and hit the ledge to collect the heart.

Spark Mandrill's Stage:
When you see a ladder going down, climb on to the wall next to it. Dashjump from the wall, and try to reach the ledge above you or try and grab the heart with the Boomerang (Boomer Kuwanger's weapon).

Launch Octopus's Stage:
When you reach the area with cyclones coming out of the water, use one to get to the top to jump on the ship and destroy it. It should crash through the ground and lead you to another area. Defeat the snake inside to goto the next area and collect the heart.

Storm Eagle's Stage:
At the start of the level, ride the lifts up to the top. When you reach the very top, dashjump to the left. You should be able to reach the top and get the Heart Tank

Flame Mammoth's Stage:
You have to kill Chill Penguin before you get this. When you get ot the part where the miners are throwing pick axes at you just keep going to the right on the frozen lava and pick up the heart tank.

Armored Armadillo's Stage:
When you reach the second spike tank, use the Fire Wave destroy it ASAP or quick buster shots. You should be able to reach the heart if you destroyed it quickly.

Wheel Gator's Stage:
After the section with the robot ride armor, you see a heart on a platform with spikes on the side. Stand on the first platform on the right, jump, air dash, and use the charged up speed burner (If you don't have these upgrades/weapon you can't get it)

Wire Sponge's Stage:
At the beginning of the level just climb the left wall and pick it up

Overdrive Ostrich's Stage:
This one is tricky, you have to have the bike you pick up before the sandstorm generator and go a good ways destroying men and knocking over little miniramps and generally avoiding falling into holes, walls. When you jump your first ledge in the building you'll come up to a part where there's nothing but spikes on the ground along with the heart container next to a wall full of spikes, go ahead and get the heart container, if you die who cares! If you can't get it with the bike just do the same thing needed to get the Heart Tank at Wheel Gator's stage

Flame Stag's Stage:
When you're climbing up the area with the rising lava you'll notice the heart tank is blocked by a robot pillar - quickly destroy it and pick up the heart before the lava reaches that level

Magna Centipede's Stage:
After the first set of alarms, go forward a bit until you reach the blocks. Go back to see a block near an upward passage. Jump and dash then use the charged up speed burner to reach the wall, climb it to get the heart (Don't set the alarms off or you don't have a chance)

Bubble Crab's Stage:
Get to the horizontal gate before the fish. Climb up the right wall, and air dash over to a missile-platform (you have to jump around on a few of the missiles). Use this to get to the heart.

Morph Moth's Stage:
On the second shield robot in the stage, use Crystal Hunter. Use him as a step to get to the roof and pick the heart up.

Crystal Snail's Stage:
At the beginning of the stage, grab the Robot Ride Armor, and head back a bit to the first pit and fall in. Jump Dash with the robot and when it starts to fall eject out and use the strike chain (hope you grab a wall) to pull yourself over and get the heart.

Toxic Seahorse's Stage:
Early in the stage, you'll have to climb up through sewer, go to the very top to find the Heart Tank.

Blast Hornet's Stage:
You'll find this one soon after you encounter Doppler's aircraft. Right after that part, you should see a wall that's a bit off the ground. Air dash straight up and jump up the wall to get the Heart Tank there.

Gravity Beetle's Stage:
Once you defeat Blast Hornet, the crates in the first hangar will be gone. When you enter the hangar, head to the upper-left corner to find the heart tank.

Neon Tiger's Stage:
This Heart Tank is right above the boss gate. Use the flying bug platform and dash jump off of it to reach the heart.

Blizzard Buffalo's Stage:
Right after you find the robot ride platform, there some large ice blocks. Use either N or K Armor to smash through them to find the heart tank.

Volt Catfish's Stage:
When you reach the second lift, ride it to the top. There should be a room on the right (where the heart tank is). Air dash to it to avoid spikes.

Crush Crawfish's Stage:
Go to the robot ride platform right at the beginning of the level and choose the N, K, or H mech. Continue on, and you will see a robot fall through a couple layers of scafolding. One of the walls on the right is weak, so use the mech to smash through it. The Heart Tank is in there.

Tunnel Rhino's Stage:
A bit after the start of the stage there is a small room with a boulder tied to the ceiling. Use a charged Triad T. attack for bring the rock down to get to the heart.