Aquarium Spray Paint!!

Don't waste your time, if it takes sandpaper to remove it, it has adhered to the plastic and will stay there. Plastic is an easy thing for paints to adhere to unlike metals which require much more surface preparation. If it takes all that get a new piece of PVC and save yourself all the work of removing the paint.

 

Again not trying to burst anyones bubble but if you put that stuff in saltwater you wont need sandpaper. I do custom paint for a living and plastic is by far one of the hardest things to correctly prep and make paint stick to for an extended period of time. Not saying its going to peel off in 5 minutes but sooner or later (probably sooner) it will come off. $3 spray paint does not have the chemical make up to withstand being submerged in saltwater or any water for that matter. If its on PVC or polypropeline your chances of it lasting are even thinner. Again not trying to be blunt or push anyones buttons but 99% of aerosol paints have no business being applied on anything that will come in contact with your fish. Just trying to save you some time and cash.

 

i would just sand off the old paint and repaint with fusion. ive got it and it works wonders!