The Ultra High Capacity Tank is an advanced upgrade in Subnautica: Below Zero that’s tucked behind a few hurdles. It adds a whopping 180 units of air capacity to the player’s suit, which should make underwater exploration a bit safer. It’s also one of the first upgrades that force players to venture out into the unknown depths where all sorts of the weird and wonderful await them. This guide will help you gather all of the Ultra High Capacity O2 Tank’s in Subnautical: Below Zero in no time at all.
Ultra High Capacity O2 Tank blueprint location in Subnautica: Below Zero
Screenshot by PC Invasion
Fragments for this O2 Tank upgrade can be found in Sea Monkey Nests. A cluster of them can be found in a Lilypad Crevice biome located 1200m southeast of the drop pod. Before setting out to search for this upgrade, players will want to get a Seatruck with Depth Upgrade MK1 since the nests are located roughly 220m below sea level. Also, consider getting the Afterburner upgrade to help evade the many Squidsharks in the area.
Screenshot by PC Invasion
Look for the ancient device with the segmented cable and blinking light pictured above, then dive down the cavern to its right to find the first nest. After that, explore the rest of the cavern to get to the other ones. The Sea Monkey Nests are relatively close to each other, so spotting them shouldn’t be too hard. Fragments of the Ultra High Capacity Tank should be stuck around the outer edges of the nests themselves.
How to craft the Ultra High Capacity Tank in Subnautica Below Zero
Screenshot by PC Invasion
To craft the upgraded tank, players will need to have a Modification Station installed in their base, as well as 4x Lithium and a pre-built High Capacity Oxygen Tank, which serve as crafting ingredients. All of these require a fair bit of exploration outside the safety of the drop pod’s immediate vicinity, but they won’t ask players to venture as far out as the Ultra High Capacity Tank’s location, thankfully.
Lithium can be found just sitting on the ocean floor. The fastest way to get a ton of these is to head to the Purple Vents biome, which is about 700m southeast of the drop pod. There should be several Lithium chunks around the vents themselves. Be careful though, as there is usually a Cryptosuchus (or several) patrolling the area.
As for the High Capacity Oxygen Tank, explore the trench in the Twisty Bridges biome 300m south of the pod. There is a databox next to some abandoned cargo crates and a derelict base module about 125m below sea level. Craft this upgrade with a Standard O2 Tank, 2x Glass, 1x Silver Ore, and 4x Titanium.
Lastly, to get the Modification Station blueprint, head directly north of the drop pod until you reach the base of the landmass beyond. Hug the wall, then keep swimming eastward you find the large pocket past the giant icicles. Emerge from the water and exit the cave to find Outpost Zero. A ruined Modification Station can be found inside along with some other useful items. This is only one of the many Alterra facilities that players can explore in Subnautica: Below Zero
