Battle Arena

Battle Arena is a mode in Bloons TD Battles Mobile that was soft-released for Android on August 19, 2015 and fully released for iOS on August 25, 2015. It involves different leagues, and the player can enter any. They cost medallions, and each league has a different medallion cost. At the tower selection screen, your medallions along with your opponent's are then placed in a trophy and a map is picked. There is different rules in an arena (including but not limited to Free Boosts, Classic, etc.). You then battle with that rule chosen. Whoever wins the battle will take all the medallions. You can rematch if you'd like, but your opponent must accept. If you rematch, then your medallions are taken to the trophy and the same rules follows.

Your medallions you earned are placed in a Weekly Leaderboard (take note rematches does not count). You qualify for it once you win 100. Staying in a certain position can win you medallions at the end of that week. Afterwards, the Weekly Leaderboards are then reset.

Leagues
There are different types of leagues, all costing differently. Be aware that if you go on a higher rank, you will be taking risk of your medallions if you lose.
 * Yellow Stadium: Costs 5. You can play for free if the update 3.2 is installed and you watch an ad. A basic league for players starting out or players who don't want to lose their medallions. Like any arena, a win will give you all the medallions spent to get in, giving you 10 and making your opponent lose 5. It is the opposite if you lose the battle.
 * North Pole: A replacement for the regular Yellow Stadium arena on December 14, 2015. It costs the same to enter, but you win 15.
 * White Wasteland: Costs 20. An intermediate league that is used normally. If you win, you earn 40.
 * Winter Wonderland: Another replacement for the regular White Wasteland arena on December 14, 2015. It costs the same to enter, but you win 50.
 * Lead Dungeon: Costs 100. This league is used if you want to win tons of medallions. If you lose, you will lose100, so be careful. However, if you win, you win a whopping 200. If you want to earn the COBRA more safely, use this league.
 * Rainbow Ruins: Cost 500. Also commonly used to get the COBRA faster. If you win, 1,000 are added to your bank, but be careful as 500 are not easy to collect.
 * Ceramic Crucible: Cost 2,000. This is a very high rank of the leagues and winning a battle gives you 4000. Entering is a serious risk, though, since you'll have to earn back two thousand medallions if you lose.
 * MOAB Pit: Cost 10,000. This is open only during the second to last day in a week in Battle Arena, and lasts 48 hours. Know that losing will cost you 10,000, so only enter if you're sure you can win. You will win 20,000 if you win, though, so winning will give you a big payoff.
 * Before update 3.2, MOAB Pit only costed 5,000 and winning would've provided 10,000. It also was open on the last day of the week and lasted 24 hours like BFB Colosseum.
 * BFB Colosseum: Cost 25,000. It is only open during the last day of a week in Battle Arena and lasts 24 hours. You are advised that it costs tons of medallions and losing will rip you off on 25,000. Only enter if you know you're going to win, and if you do, you will win 50,000!

Club Arenas
On update 3.2, Club Battles were open in Battle Arena and Assault Mode. They include special rules including but not limited to random towers being your default towers and other rules. The apply to only a certain number of arenas. Unless you pay $4.99 USD to join the club, you may only play one club game per 24 hours. On update 3.3, Combo Arenas were open and were just two of these arenas combined.


 * Bananza: Every method of cash and economy generation is twice their regular amount, making expensive towers easier to buy. Recommended towers includes Banana Farms, Super Monkeys, Heli-Pilots, or anything powerful. Be ready for late game, as double the cash will make late game more common.
 * Random Trio: You will be selected a random tower selection and you will be unable to use a bonus tower. You must be wise with your towers and rush if you see a weakness to win this club battle. If your towers cannot reliably detect Camo Bloons, skip the map or else you will easily lose the game unless you rush first to your opponent.
 * Playing With Fire: Bloon economy increasements/decreasements are doubled, but any bloon you send to your opponent is also sent to your side. Be sure you can defend the rush you send or you might lose. Banana Farms and COBRA farming is not recommended as bloon eco gives 2x income and is preferred.
 * Mega Boosts: Tower Boost upgrades all towers on the path with the most upgrades, while Bloon Boost temporarily upgrades all Bloons by 1 rank. This can be very powerful, even if you have high level towers. If you are unable to defeat your opponent with rushes, your best bet is to kill your opponent on level 20 or 23 with a Bloon Boosted (Fast Cooldown) BFB rush, which will spawn ZOMGs that would lead to the opponent's easy defeat.
 * Speed Battles: Bloons moves faster, players can send bloons two rounds earlier and players' income generates every 4 seconds instead of 6 seconds. Make sure your strategy is good, as even on short maps this could be the hardest Club Battle. Recommended towers includes Monkey Engineers, Ninja Monkeys, and Super Monkey due to their fast attack speed.

Strategies

 * There are some very good players in the Arenas. If you are new to the game or lack strong towers/upgrades, Yellow Stadium is good, since it is a low-stakes arena. Higher-stakes arenas are not a good idea until you have plenty of skill.
 * Remember how many medallions you have. Unless you're a very good player with a lot of medallions, stay away from higher-tier arenas.
 * Recommended towers for normal games include Dart Monkey, Banana Farm, Monkey Sub, Monkey Engineer, Bloonchipper and COBRA. See above for club games.
 * If it is free power-ups, use them wisely. You and your opponent have only 3 tower and bloon boosts, try to make your opponent waste theirs early on by sending bloons that will cause them to use the tower boost in panic.
 * If it is classic, try to stock or save on battle energy as you might need it later.
 * You aren't the only one reading this guide. Prepare for your opponent having the towers mentioned above.
 * Try to rank high in the leaderboards so you can get many medallions, even enough for a COBRA!
 * Even if you make one mistake or get disconnected during the game, it can make you lose the game later on.

Trivia

 * All the arenas are named after bloons: Yellow, White, Lead, Rainbow, Ceramic, M.O.A.B, and B.F.B.
 * If you play Mega Boosts Arena or battle and you try to upgrade Sun Gods into Temples via Monkey Boost, every Temple will be sacrificed and disappear after the animation and will lead you to a very easy defeat or if you can survive, waste of cash. It can be seen here. As a result, Super Monkeys should be best upgraded on path 2 where it can easily be upgraded to Robo Monkey or Technological Terror or be manually upgraded. This is now patched.
 * If you play Mega Boosts and use the monkey boost on towers, it will upgrade the tower's "most advanced" path.