I'm assuming it's not a solid blue acrylic panel as is the industry norm. You cannot use any solvents to remove paint from acrylic since solvents will either craze or soften acrylic plastic. The only safe method is laborious at best. The paint must be wet sanded from the acrylic. Then, the entire panel must be wet fine-sanded and polished back to clear.
Your best bet is to trade it or sell and replace the tank.
Thanks for the info, guys!
I'm keeping it!! It is another 300 g.
And no, it's not the solid blue panel - it's been painted over - I guess I'll just leave it as is. It doesn't bother me too much - if there were an easy way, I would.
Thanks again!