Short answer: the best upgrade path for Sub in BTD6 depends on the job. Build 2-0-2 early, then pick Path 2 (Pre-emptive Strike) for MOAB-class defence or Path 1 (Energizer) for cooldowns and hero XP.
This guide shows the real costs, the trade-offs, and one build for each goal.
Quick Answer: Which Sub Build Fits Your Goal?
Prices below use Medium difficulty. Costs come from the total-cost table on the Blooncyclopedia Monkey Sub page.
| Goal | Build | Total cost |
|---|---|---|
| Early-game defence | 2-0-2 | $2,405 |
| Cheap camo detection | 3-0-0 | $1,655 |
| Camo detection plus Lead popping | 4-2-0 | $4,805 |
| Ability cooldowns and hero XP | 5-0-0 | $32,055 |
| MOAB-class and DDT defence | 0-5-0 | $44,425 |
| Damage buff for other Subs | 0-0-5 | $30,375 |
How We Checked This Guide
We pulled every number from the Bloons wiki community pages and cross-checked them against each other. We did not invent stats or use guesses.
- Costs and upgrade text: Blooncyclopedia.
- Tier 5 details: the Blooncyclopedia pages for Pre-emptive Strike and Energizer.
- Strategy notes: the Fandom Monkey Sub strategy page.
- Checked: 24 September 2026. Patches change numbers, so verify in-game before a big run.
Tier prices are the gap between two rows of the wiki's total-cost table, so treat them as calculated values.
Monkey Sub Basics You Need First
- The Sub is a Military tower that fires seeking darts that pop up to 2 Bloons.
- It attacks every 0.75 seconds and works only on water.
- Base price: $275 Easy, $325 Medium, $350 Hard, $390 Impoppable.
- Path 1 covers range and support. Path 2 covers missiles. Path 3 covers guns and team buffs.
Full Monkey Sub Upgrade Costs (Medium)
| Tier | Path 1: Support | Path 2: Missiles | Path 3: Guns |
|---|---|---|---|
| 1 | Longer Range, $130 | Barbed Darts, $450 | Twin Guns, $450 |
| 2 | Advanced Intel, $500 | Heat-tipped Darts, $300 | Airburst Darts, $1,000 |
| 3 | Submerge and Support, $700 | Ballistic Missile, $1,350 | Triple Guns, $1,100 |
| 4 | Bloontonium Reactor, $2,400 | First Strike Capability, $13,000 | Armor Piercing Darts, $2,500 |
| 5 | Energizer, $28,000 | Pre-emptive Strike, $29,000 | Sub Commander, $25,000 |
Derived from the total-cost table on Blooncyclopedia. Excludes Monkey Knowledge and other discounts.
Early Game: Build 2-0-2 First
Blooncyclopedia says early Subs generally build toward 2-0-2. Homing darts and long reach handle early rounds well.
- Cost: $2,405 on Medium.
- Upgrades: Longer Range, Advanced Intel, Twin Guns, Airburst Darts.
- Why it works: Advanced Intel lets the Sub hit Bloons near your other towers.
- Bonus: a Berserker Brew doubles its damage and pierce, per the same wiki page.
Path 1: Support Subs (Submerge, Reactor, Energizer)
Submerge and Support (3-0-0)
This upgrade turns the Sub into a camo detector. The Fandom strategy page calls it a cheaper way to reveal Camo Bloons than Radar Scanner or Shimmer.
- Total cost: $1,655 on Medium.
- A submerged Sub cannot throw darts.
- Add Heat-tipped Darts (4-2-0) to cover Lead Bloons, per the same strategy page.
Energizer (5-0-0)
Energizer is expensive, but it changes the whole map. It cuts ability cooldowns everywhere by 20%, and by 40% for water-based Monkeys, according to Blooncyclopedia.
- Heroes in its radius earn XP 50% faster.
- Blooncyclopedia notes it is common with Admiral Brickell and Psi.
- The Energizer page calls it strongest in Freeplay and against Boss Bloons.
Path 2: Missile Subs (Ballistic, First Strike, Pre-emptive)
Path 2 is the MOAB-killer branch. Ballistic Missile flies over walls and deals extra damage to MOABs and Ceramics.
Pre-emptive Strike (0-5-0)
- It fires one 750-damage missile at every MOAB-class Bloon that enters the map.
- Its First Strike cooldown drops from 45 to 30 seconds.
- Paired with Sub Commander, it can one-shot Round 99 DDTs.
- The catch: it stays weak against Super Ceramics, per the same page.
Silas benefits too. Blooncyclopedia says Pre-emptive Strike covers DDTs and the BAD well for him.
First Strike Capability (0-4-0)
First Strike gives you an ability that hits the largest Bloon on screen. Blooncyclopedia says it can layer-skip the BAD's insides once the BAD has taken enough damage.
Path 3: Gun Subs and Sub Commander
Path 3 raises attack speed and pierce. Sub Commander then doubles damage and adds +4 pierce for Subs in range, including itself.
- The Monkey Knowledge "Sub Admiral" extends that buff to every Sub on screen.
- Blooncyclopedia warns that it struggles late compared with more efficient options.
- It is also weak to Super Ceramics.
- Use it with a Pre-emptive Strike Sub, not as a lone star.
Tier 5 Cost Compared
Common Sub Mistakes
- Buying Energizer too early. It pays off when you run many abilities.
- Expecting a submerged Sub to attack. It only reveals camo and supports.
- Relying on Sub Commander alone. Late rounds punish it.
- Skipping Advanced Intel. Blooncyclopedia rates Heat-tipped Darts weak without it, since range suffers.
- Placing on the wrong tile. Subs only go on water. Yes, the monkey knows.
Frequently Asked Questions
What is the cheapest camo detection on a Monkey Sub?
Submerge and Support (3-0-0) costs $1,655 on Medium. It reveals camo without a second tower.
Which Sub helps heroes level faster?
Energizer. Heroes inside its radius earn XP 50% faster, according to Blooncyclopedia.
Is Sub Commander worth it?
Only in a Sub-focused team. It doubles damage for nearby Subs but falls behind other late-game options.
Do Sub prices change by difficulty?
Yes. The base Sub costs $275 on Easy, $325 on Medium, $350 on Hard, and $390 on Impoppable.
Does the best Sub path change after patches?
It can. Pre-emptive Strike, for example, has had several rebalances, so recheck the wiki before a big run.
Keep Reading on GMRU
Playing BTD6 on a computer? These guides can help you get smoother frames.
- PC for Gaming vs Gaming Laptop: Value, Performance and Upgrade Potential
- How to Upgrade and Maintain a Refurbished Gaming PC
- How a High-Performance Gaming Monitor Improves Your Gameplay
Sources
Short answer: the best upgrade path for Sub in BTD6 depends on the job. Build 2-0-2 early, then pick Path 2 (Pre-emptive Strike) for MOAB-class defence or Path 1 (Energizer) for cooldowns and hero XP.
This guide shows the real costs, the trade-offs, and one build for each goal.
Quick Answer: Which Sub Build Fits Your Goal?
Prices below use Medium difficulty. Costs come from the total-cost table on the Blooncyclopedia Monkey Sub page.
| Goal | Build | Total cost |
|---|---|---|
| Early-game defence | 2-0-2 | $2,405 |
| Cheap camo detection | 3-0-0 | $1,655 |
| Camo detection plus Lead popping | 4-2-0 | $4,805 |
| Ability cooldowns and hero XP | 5-0-0 | $32,055 |
| MOAB-class and DDT defence | 0-5-0 | $44,425 |
| Damage buff for other Subs | 0-0-5 | $30,375 |
How We Checked This Guide
We pulled every number from the Bloons wiki community pages and cross-checked them against each other. We did not invent stats or use guesses.
- Costs and upgrade text: Blooncyclopedia.
- Tier 5 details: the Blooncyclopedia pages for Pre-emptive Strike and Energizer.
- Strategy notes: the Fandom Monkey Sub strategy page.
- Checked: 24 September 2026. Patches change numbers, so verify in-game before a big run.
Tier prices are the gap between two rows of the wiki's total-cost table, so treat them as calculated values.
Monkey Sub Basics You Need First
- The Sub is a Military tower that fires seeking darts that pop up to 2 Bloons.
- It attacks every 0.75 seconds and works only on water.
- Base price: $275 Easy, $325 Medium, $350 Hard, $390 Impoppable.
- Path 1 covers range and support. Path 2 covers missiles. Path 3 covers guns and team buffs.
Full Monkey Sub Upgrade Costs (Medium)
| Tier | Path 1: Support | Path 2: Missiles | Path 3: Guns |
|---|---|---|---|
| 1 | Longer Range, $130 | Barbed Darts, $450 | Twin Guns, $450 |
| 2 | Advanced Intel, $500 | Heat-tipped Darts, $300 | Airburst Darts, $1,000 |
| 3 | Submerge and Support, $700 | Ballistic Missile, $1,350 | Triple Guns, $1,100 |
| 4 | Bloontonium Reactor, $2,400 | First Strike Capability, $13,000 | Armor Piercing Darts, $2,500 |
| 5 | Energizer, $28,000 | Pre-emptive Strike, $29,000 | Sub Commander, $25,000 |
Derived from the total-cost table on Blooncyclopedia. Excludes Monkey Knowledge and other discounts.
Early Game: Build 2-0-2 First
Blooncyclopedia says early Subs generally build toward 2-0-2. Homing darts and long reach handle early rounds well.
- Cost: $2,405 on Medium.
- Upgrades: Longer Range, Advanced Intel, Twin Guns, Airburst Darts.
- Why it works: Advanced Intel lets the Sub hit Bloons near your other towers.
- Bonus: a Berserker Brew doubles its damage and pierce, per the same wiki page.
Path 1: Support Subs (Submerge, Reactor, Energizer)
Submerge and Support (3-0-0)
This upgrade turns the Sub into a camo detector. The Fandom strategy page calls it a cheaper way to reveal Camo Bloons than Radar Scanner or Shimmer.
- Total cost: $1,655 on Medium.
- A submerged Sub cannot throw darts.
- Add Heat-tipped Darts (4-2-0) to cover Lead Bloons, per the same strategy page.
Energizer (5-0-0)
Energizer is expensive, but it changes the whole map. It cuts ability cooldowns everywhere by 20%, and by 40% for water-based Monkeys, according to Blooncyclopedia.
- Heroes in its radius earn XP 50% faster.
- Blooncyclopedia notes it is common with Admiral Brickell and Psi.
- The Energizer page calls it strongest in Freeplay and against Boss Bloons.
Path 2: Missile Subs (Ballistic, First Strike, Pre-emptive)
Path 2 is the MOAB-killer branch. Ballistic Missile flies over walls and deals extra damage to MOABs and Ceramics.
Pre-emptive Strike (0-5-0)
- It fires one 750-damage missile at every MOAB-class Bloon that enters the map.
- Its First Strike cooldown drops from 45 to 30 seconds.
- Paired with Sub Commander, it can one-shot Round 99 DDTs.
- The catch: it stays weak against Super Ceramics, per the same page.
Silas benefits too. Blooncyclopedia says Pre-emptive Strike covers DDTs and the BAD well for him.
First Strike Capability (0-4-0)
First Strike gives you an ability that hits the largest Bloon on screen. Blooncyclopedia says it can layer-skip the BAD's insides once the BAD has taken enough damage.
Path 3: Gun Subs and Sub Commander
Path 3 raises attack speed and pierce. Sub Commander then doubles damage and adds +4 pierce for Subs in range, including itself.
- The Monkey Knowledge "Sub Admiral" extends that buff to every Sub on screen.
- Blooncyclopedia warns that it struggles late compared with more efficient options.
- It is also weak to Super Ceramics.
- Use it with a Pre-emptive Strike Sub, not as a lone star.
Tier 5 Cost Compared
Common Sub Mistakes
- Buying Energizer too early. It pays off when you run many abilities.
- Expecting a submerged Sub to attack. It only reveals camo and supports.
- Relying on Sub Commander alone. Late rounds punish it.
- Skipping Advanced Intel. Blooncyclopedia rates Heat-tipped Darts weak without it, since range suffers.
- Placing on the wrong tile. Subs only go on water. Yes, the monkey knows.
Frequently Asked Questions
What is the cheapest camo detection on a Monkey Sub?
Submerge and Support (3-0-0) costs $1,655 on Medium. It reveals camo without a second tower.
Which Sub helps heroes level faster?
Energizer. Heroes inside its radius earn XP 50% faster, according to Blooncyclopedia.
Is Sub Commander worth it?
Only in a Sub-focused team. It doubles damage for nearby Subs but falls behind other late-game options.
Do Sub prices change by difficulty?
Yes. The base Sub costs $275 on Easy, $325 on Medium, $350 on Hard, and $390 on Impoppable.
Does the best Sub path change after patches?
It can. Pre-emptive Strike, for example, has had several rebalances, so recheck the wiki before a big run.
Keep Reading on GMRU
Playing BTD6 on a computer? These guides can help you get smoother frames.
- PC for Gaming vs Gaming Laptop: Value, Performance and Upgrade Potential
- How to Upgrade and Maintain a Refurbished Gaming PC
- How a High-Performance Gaming Monitor Improves Your Gameplay