Monkey Bank (BTD6)

"All money generated by this farm is now stored in the bank and earns 15% interest every round."

- In-game description

Monkey Bank is the 3rd upgrade on Path 2 for Banana Farm in Bloons TD 6. When a Banana Farm gets upgraded to Monkey Bank, the farm becomes a bank controlled by monkeys. The Monkey Bank no longer drops bananas but instead generates money throughout the round, which is placed in its very own "bank account", separate from that of other Monkey Banks.

It generates $230 per round which can be upgraded to $270 and $310 with the Increased Production and Greater Production upgrades, respectively. It can store up to $7,000 and its capacity can be increased to $9,500 with the Bigger Banks Monkey Knowledge. At the end of each round, the currently stored balance earns 15% interest. Therefore, a Monkey Bank can produce at least $265 per round at bare minimum when interest is taken into consideration.

Despite Path 3 upgrade crosspaths not seeming to be useful at increasing income, Path 3 upgrade crosspaths have utility usage. Monkey Bank with EZ Collect will highlight itself once it is full, while a Monkey Bank with the Banana Salvage upgrade will autocollect its balance when full after one round, on top of +10% sellback.

Unlike BTD5, selling a Monkey Bank will automatically withdraw the balance stored in the bank.

It costs $2,975 on Easy, $3,500 on Medium, $3,780 on Hard, and $4,200 on Impoppable.

Tips

 * 2-3-0 is usually far superior over 0-3-2, due to the 2-3-0 Bank's far greater income gain per round. 0-3-2 is still a very viable option once a decent income flow begins, as the top path may cost user hassle compared to the benefit of automatic withdrawals from Banana Salvage.
 * A single 0-3-X Monkey Bank will reach maximum capacity at the same time as a 2-4-0 IMF Loan in almost all conditions. If you're upgrading your banks to IMF Loan, having a 0-3-1 Monkey Bank helps to indicate when all banks are full without having to check them every so often.
 * The "Bigger Banks" (+$2500 bank capacity) Monkey Knowledge is a very important MK for maximizing the potential of Monkey Bank farming.
 * Whenever using Monkey Banks, always try pairing with Benjamin. On later upgrades, Level 5+ and 9+, he grants +5% and +12% income for banks, respectively.
 * Benjamin's "interest" buff appears to be erroneous. He apparently does not actually buff the interest rate, but rather improves the total value of the automatic deposits per round by a set percentage.
 * To calculate Benjamin's "interest" buff, multiply the current round's automatic deposit amount by 1.05 or 1.12, respectively, rather than adding percentages into the Bank's natural 15% interest. To reiterate, the Benjamin "interest" buff only affects the automatic deposits per round.
 * It is worth studying the rounds in the game, in order to prepare necessary defenses against possible difficult rounds and therefore reduce the risk of forcing out the bank investment too soon.

Summary
Monkey Bank's main prowess comes from storing cash over long periods of time. When stored until max capacity, the Monkey Bank becomes one of the most efficient income producers in the entire game. In order to make the most of the Monkey Bank, it is best placed as early as possible but at the same time having a relatively stable long-term defense. Between Rounds 20-30 is generally the best time to start off the first Monkey Bank.

The main disadvantage of the Monkey Bank, however, is that early withdrawals harm its overall income generation efficiency. By having a good defense, the player will be able to keep the Monkey Bank's bank account stored for longer periods, for a far better reward in the long run.

Generally, one should buy more and more banks rather than purchase IMF Loan (or most other income sources, even). This is in order to capitalize on Monkey Bank's incredible efficiency, which is almost incomparable to most other income sources in the game.

Efficiency

 * Current information provided is (currently not) valid starting from Version 26.0, with the buff to Monkey City giving automatic deposits with +15% income instead of +10%.
 * For all income earnings per round in history, including current and past income earnings per round, see Monkey Bank (BTD6)/Efficiency.

Income earning per round (26.0-Present)
As of Version 26.0, Monkey City now has its bonus income buff improved from +10% to +15%, which subsequently changed the total stored income for Banks with City buff compared to without. Otherwise, Banks without that buff are the same.

Note: The table assumes that the Monkey Bank has been initially upgraded before the first round starts and that the result is given as when the round has ended. (After interest has been applied)

Also assumes that the Bigger Banks MK is active.

And with City buff:

TBA



Trivia

 * On Version 14.0 and later, Monkey Banks and their subsequent upgrades do not make bank collection sounds when collecting their accounts.
 * Interestingly enough, the autocollection from crosspathing with Banana Salvage didn't make an autocollection sound either, even before Version 14.0.
 * The name "Monkey Bank" is a play on "money bank".
 * According to Ninja Kiwi's May 7th 2021 blog, the monkeys inside Monkeys Banks profit by means of investing on "quantum markets". Automatic depositing in the Monkey Bank apparently allows monkeys investing on those markets to profit even within a short amount of time of leaving their deposits in the Bank. The same should apply to manual deposits, although it will take one additional round after depositing before the interest of manual deposits can begin due to the Version 19.0 Bank Deposits nerf.
 * Monkey Bank has the only upgrade icon that represents a non-mythical animal other than monkeys. In this case, that upgrade icon features a pig, representing a piggy bank.

Other Sources

 * Qwertyxp2000's PDF of Monkey Bank efficiencies by version ([[File:BankBloonsTD6-23.pdf]]).