I agree w/ toirtis.
Eheim Classics are the way to go.
The reduced flow rate is fine, because the bio load of the classics are huge.
Which more than makes up for the lack of flow.
I Eheim
Try going to a place where they work on boats. Marine paint is a excelent sealer, and is aquarium safe.
Although the pool paint might work. You'll have to check that out.