Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Glass tank, use paint for glass. It will run or streak less and dry faster than paint not intended for glass. Acrylic tank- a paint for plastics is probably best.
Since the paint is on the exterior of the tank there is no toxicity problem. It will be fully dry when you set up the tank.
You can use any application sort, spray paint, brush on...
You can use specialty paints like crackle effect (VERY slow to dry)
Tape off and mask ALL parts where you do not want paint. Spray paint tends to go ALL OVER, so mask it ALL. Brush on is more controlled, but I would still mask the parts next to the edges of the paint. Makes a much cleaner edge.
If spraying move steadily back and forth over the area, applying the paint in several thin coats. Start the spray before you are aiming at the tank. Read the label for drying time between coats.
Similarly, brush or roll on thin layers, wait for it to dry, then apply a second or third coat.
If you are using a specialty material like the crackle effect read and follow the directions carefully.
If you are thinking about paints or other coloring materials used to create DIY backgrounds that are inside the tank, this is different. Find instructions at a fish site for the type of background you are making, and follow the instructions, including the brand of paint or other coloring used. There are some really nice projects out there!
I have used Krylon Fusion for Plastic on some PVC pipe inside a tank. It is holding up fairly well, though not 100%. I forget how many years it has been in place.