Tank 5-1 or the Final Boss Fight is the 21st and final level of Insaniquarium. In this stage, you have to protect all your pets so far (except Angie, Presto if already acquired, and the four bonus pets) against the evil alien mastermind, Cyrax.
See Cyrax for more information.
Your laser is automatically upgraded to level 8 in this level. Though Cyrax can't eat your pets directly, it's still a tough fight, as he can summon all the aliens you've fought before, plus a new alien, Mini-Sylvester, a fast little creature that is a miniature version of Sylvester. You have to keep pounding Cyrax while defeating the Mini-Sylvesters and a multitude of aliens he summons. At least one pet must survive the fight in order to win the level. Once completed, you get Presto, who began hatching before the fight, and you get 5000 shells. If you have already finished Adventure Mode once, you get more shells as an extra reward instead. The multi-defeat reward ranges from 10000-25000, depending on how many times you've beaten Cyrax (10000 shells for 2 times, 15000 for 3, 20000 for 4, and 25000 for 5 and more times).
The most common and effective strategy is the Destructor Method (that is if you want to save most of your pets). The moment Destructor is summoned, do not destroy it; only neutralize its missiles. Lead Cyrax as far away from it as possible, so that it won't get caught in your blasts. Plus, Cyrax won't summon any other alien as one is already in the tank. Destructor won't pose as much of a threat because it doesn't eat your pets directly, and its missiles aren't as dangerous as Ulysses' blasts. So just keep shooting at Cyrax, while killing the Mini-Sylvesters and destroying Destructor's missiles. If done right, most of your pets may survive. You don't even have to worry about killing Destructor after the battle, as after Cyrax is destroyed Destructor will "self-destruct" and die with him.
After the fight, the credits will roll in:
You've successfully vanquished the alien hordes!
The epic conflict between fish and evil has finally come to a close.
Thanks to you, aquarium owners can sleep easy tonight!
Many a pet gave their lives in the final battle, but do not grieve, little one!
Angie purposefully sat out of the fight, and word is she's got a few tricks up her sleeves...And at this point, Angie will revive all the Pets that died during the final fight. With that, a message is shown, depending on how many pets you saved.
If you saved 1 - 7 pets:
"Thanks for playing. We'll See You Again Next Game"
If you saved 8 - 12 pets:
"Also, you saved a fair number of pets yourself. Good job! Thanks For Playing. We'll See You Again Next Game"
If you saved 13 - 14 pets:
"Hmmm... actually it looks like not that many pets died. Great work!! Thanks For Playing. We'll See You Again Next Game"
If you saved 15 pets:
"Whoa, hold on... Only 3 pets died?! That's incredible! Good shooting, there! Thanks For Playing. We'll See You Again Next Game"
If you saved 16 pets:
"Whoa, hold on... Only 2 pets died?! That's incredible! Good shooting, there! Thanks For Playing. We'll See You Again Next Game"
If you saved 17 pets:
"My goodness! That's it? You only lost one pet?! That's unbelievable!! How the heck did that happen? You rule this game!! Thanks For Playing. We'll See You Again Next Game"
If you saved all 18 pets:
"Wait a minute! You didn't lose any pets?! How did you do that? That's really amazing! Seriously though... How did you do that?? Fine, keep it to yourself! Thanks For Playing. We'll See You Again Next Game"
- Attacker pets (Itchy, Rufus, and Gash) will not attack the aliens.
- The health of Cyrax will be shown all the way, even if Blip is already dead. Blip will not show anything else.
- Gumbo's lantern will still flash, but only when the other aliens are summoned (excluding Mini-Sylvester).
- Stinky will hide in his shell when an additional alien appears, but oddly not while Cyrax is present.
- When an alien (not including Mini-Sylvester) is summoned, Itchy's expression will be his angry face. It will return to normal once the summoned alien or Cyrax is killed.
- Any aliens left over after Cyrax is defeated will automatically die.
- When all the pets are killed by aliens or Mini-Sylvester, the losing message says "Oops! All of your pets (instead of fish) died!" will appear.
- You will battle a man in a UFO in Insaniquarium: Revenge of the Fish instead, which takes the place of Cyrax.