I guess the title says it all but just to clarify: I have a five gallon tank that I received free from someone. It’s obvious it wasn’t well maintained bc the insides are crusted over with tons of residual gunk. There was also a partially melted sticker thermometer on the glass. I tried using just hot water, but ended up resorting to lighter fluid to get off the more tough stuff. Is this ok? Will there be any residual lighter fluid once I set up the tank that could poison invertebrates and fish?