How do you evolve tanks in Diep.io?

Level it up in Petalburg Woods.

Make sure it doesn't know any fairy type moves. Also remember that Umbreon level up at night, and Espeon level up during the day.

If you own a thunderstone, you have to use it on Pikachu to evolve it into Raichu.

Yes, helium tanks can be dangerous if they aren’t handled correctly, since they contain compressed gas. For this reason, it’s very important to recycle or dispose of them properly.

It’s not clear that Party City recycles tanks. You can call your local Party City to find out about their policy.

You will probably have to take your tanks to your local recycling center or hazardous waste disposal site.

Charmeleon evolves into Charizard at level 36.

That is impossible.

It doesn't matter what time you catch it. It does have to be nighttime to evolve it.