If there are any depletion counters on Lava Tubes, it does not untap during your untap phase. At the beginning of your upkeep, remove a depletion counter from Lava Tubes. {T}: Add {B} to your mana pool. Put a depletion counter on Lava Tubes. {T}: Add {R} to your mana pool. Put a depletion counter on Lava Tubes.