Sub Tank

A Subtank, sometimes called Sub-Tank, is a recovery item from the Mega Man X, Mega Man Zero, and Mega Man ZX series. They are usually found hidden throughout stages and will be added to inventory once picked up. Unlike their counterparts from classic Mega Man, the Energy Tank, they are not available for immediate use, nor are they removed from inventory when used. Once a subtank has been found, picking up a health item when the character is at full health will instead fill up the subtank. The amount the subtank is filled is based on the type of health recovery item picked up. Using a subtank will restore health to the player until his or her health is back at full or the subtank is empty. If the character's health is restored to full before the subtank is empty, the tank will retain the excess in the tank. Most games limit the amount of subtanks acquired to a maximum of four. However, some game modes, such as Expert in ZX Advent, or attempting to keep an A ranking in some games of the Zero series, limit the player to one subtank, or none.

W Subtank
W Subtanks are a special kind of subtank (not to be confused with the W-Tank from Classic Mega Man). They act very much the same as normal Subtanks, except they fill and restore weapons energy instead of life energy.

EX-tank
Though the EX-Tank is usually placed in the same category as Sub-tanks, it is actually quite different from the others. Picking up the EX tank allows the player to restart the game with 5 lives when he or she dies instead of the normal 3.

Mega Man X
All subtanks throughout the X series are found scattered throughout the game. They are usually hidden quite well and many require the use of a Maverick Weapon or Armor Enhancement. Others require some creative tricks like using an enemy attack to break a wall. Mega Man X-X3 had four subtanks, Mega Man X4-X7 only had 2 subtanks, but added 1 W-tank and 1 EX-Tank, and Mega Man X8 only has the 2 subtanks and 1 W-tank, but had other items that could be used to restore health. Also, finding certain Rare Metals provides subtanks with double capacity, due to the use of two characters per stage.

Obtaining a subtank in Command Mission is different. The simplest way to find one is by completing a storyline mission and defeating the boss. In addition, collecting four pieces of one subtank hidden in the dungeons rewards an extra subtank. The player begins with the game with two pre-filled subtanks and can collect a total of ten.

Mega Man Zero
Similar to the early MMX series, the MMZ series normally has access to four subtanks. However, unlike the X series, most subtanks are obtained by finding cyber elves, and then feeding them enough E-Crystals to allow them to fully transform them into subtanks. Since using cyber-elves negatively affects Zero's ranking in most of the series, perfectionists often choose to play through the Zero games, arguably the most difficult games in the series, with two or fewer subtanks. Different modes offer extra help or limitations as well. For example, Easy Mode of MMZ4 allows the player to start with 2 full subtanks, whilst Hard Mode in the same game will limit the total to only three, as one of them requires a certain condition of the weather to be set.

Mega Man ZX
There have been 4 subtanks in each of the ZX games so far. They act the same as subtanks in both MMX and MMZero. Since Cyber Elves are no longer used, they are either found hidden throughout the levels or are rewarded as a result of a sidequest. In addition, there have usually been "antique" dealers who provide the precursor to subtanks, Energy Tanks, which act exactly like their classic counterpart. However, in Expert mode of both games, SubTanks are almost non-existent. They can only be obtained in a corresponding side quest. All other Subtanks found outside of side quests are replaced with absolute health filling items.