Regen Farming


 * As of August 28, 2013, for the flash version of BTD5 only, regen farming cannot be used to gain more cash and experience than the normal amount for non-regen versions of the bloons. Though, it's possible to Regen Farm if you have the normal Regen Farming setup, and a Supply Drop sniper. The round still lasts infinite, so you can use the ability to win cash, you will earn cash slowly at the start. And buy more Supply Drops with that cash, and win more cash.

Regen farming was a method of gaining money, with high risk but high return. It is based on regenerating bloons and can only be done in Bloons TD 5 (no more on ninja kiwi), Bloons TD 5 Deluxe and Bloons TD 5 iOS. It is based on the fact that if a regenerating bloon gains a layer it doesn't give any money when popped but if it spawns 2 bloons they will give you money when popped. Ex: When a Rainbow regenerating bloon is popped, two Zebra regenerating bloons will come out and regenerate back to Rainbows, and those two Rainbows.

Method
One method is to use about 2 or 3 3/2 Monkey Apprentices with the Summon Whirlwind upgrade. The tornado from the Monkey Apprentices will blow bloons back to the start, and by the time the bloons come back the the Apprentices, they will have multiplied. This can also be done with the Tempest Tornado upgrade, but it is best to only use a single one for this, or otherwise the bloons will either get popped right away, or likely overwhelm the player's towers. Another method is to use an Ice Tower with the Arctic Wind upgrade and a Ninja Monkey with Distraction. The Arctic Wind will give time for the bloons to multiply and the Ninja Monkey will pop them and send them back to the Arctic Wind.The player can Regen Farm on rounds 31, 42, 49, 51, 56, 61, 62, 69, 72, 76, 79, and 82.

Useful Towers for Regen Farming
Blowers:


 * Summon Whirlwind: Good for blowing bloons back, use 2 or more.
 * Tempest Tornado: Like Summon Whirwind, blows much more. Use only 1 because the tempest tornados also pop the bloons as they blow them back.
 * Distraction: Recommended to get Bloonjitsu, so it blows more bloons.
 * Downdraft (iOS only): Blows the bloons below the Tower. It can be further upgraded to Support Chinook to further increase the income.

Bloon Poppers:


 * Ray of Doom: Best for popping the regen bloons. Specialty makes it more effective. Also pops camo so you can regen farm on Regen Camo Rounds.
 * Sun God: Not as good as Ray of Doom as it has a much lower Popping Power and its shots can accidentally hit the Regen Bloons at the start, ending the Farming. It can be used as an early defense until the player can buy a Ray of Doom.
 * Technological Terror: More powerful than Sun God when both of its beams are trained onto the same target, but not so good at Popping Power.
 * Ring of Fire: Many of these can destroy the Regen bloons so they don't leak.
 * Spiked Mines Factory: At least 4 or 5 of these at the exit can handle a continuous line of Rainbow Bloons, depending on the regeneration rate of bloons.
 * Glaive Lord: The Infinite popcap makes it pretty good since the Regen Rushes are very, very dense. Makes a good pair with Arctic Wind.
 * Bloonsday Device: You will need various of them, it costs a lot of Monkey Money, but it can be purchased if you have few in-game cash. It's prefered to use the ability from the end to the start.
 * You can also have 5+ tempest tornadoes to blow back and pop bloons at the very end.

Movement reducers:


 * Glue Hose: Slows bloons so they have more time to regenerate. Glue Soak required.
 * Glue Striker makes it even more effective, slowing down bloons to 30% of their normal move speed as opposed to 40% with the Glue Hose. It also has the ability to glue every bloon on screen, further increasing effectiveness.
 * Arctic Wind: Same as Glue Hose, but only affects them in range. Permafrost makes it more effective. With the level 3 Ice Fortress or a Monkey Intelligence Bureau, it can even double as a bloon popper.

Other:


 * Supply Drop Ability: Not useful for Regen Farming, but can give you additional money since the round will last for infinite.
 * Ground Zero: Good if you want to end the Regen Farming.
 * Banana Research Facility: Tempest Tornado and Ray of Doom cost a lot and you can't get them on early rounds without heavily farming. Sell all the farms before you regen farm.
 * Monkey Town: Greatly increases the amount of money that the attacking towers get you & their efficiency against the eternally spawning bloons. It can be further upgraded to High Energy Beacon to decrease the ability recharge time of all buildings in its radious.
 * 1-2 Super Monkey: Only used near the middle lines when a powerful defense is made for the regenerating bloons. Greatly increases the amount of bloons that get popped per second. It is a good idea to upgrade it to Plasma Blasts after enough bloons spawn from the regenerating bloons. Alternetivly, the player can place down a 0-3 Robo Monkey instead, or just not upgrade it at all.
 * Bomb Tower: can put it on close to make bloons regrow more easily.  You can also do a 3-2 for this purpose.
 * Monkey Engineer (Deluxe & iOS only): Can be upgraded to Bloon Trap to further increase money income. Best used in good sized amounts away from where the bloons are being popped.

Trivia

 * It is the only way of getting a Temple of the Monkey God on the sockets of power on The Crucible (Not counting premiums and the use of Cheat Engine).
 * It is also the only way of getting a Temple on Round 31.
 * You can regen farm with Black/White/Lead/Zebra/Rainbow/Ceramic Regen Bloons.
 * This is most preferred with Rainbow Bloons because they take less damage to pop then Ceramics & spawn far more children than Zebras.
 * It may crash the player's game in Bloons Tower Defense 5 iOS, if he/she takes too long on a Round.
 * A Monkey Ace with Ground Zero can instantly get rid of all of the bloons on screen, thus ending the farm.  However, this may be needed to save you, so it's a good idea to have one ready in case you are about to be overrun.
 * Using a Super Monkey Storm also gets rid of all the bloons, but Ground Zero is the better option because it doesn't use monkey money. A Rocket Storm Ability or two may also work, as they fire missles to the nearest 100 bloons, with explosion.
 * Regen farming is also a great way to get Experience Points fairly quickly.