Slime after slime

Q there is a great deal of cream-coloured slimy growth in my boat’s fuel separator: i have drained it several times, but more keeps coming through. What is it, and how do i get rid of it, please?

STU DAVIES REPLIES: It sounds like you have the dreaded diesel bug. Bacteria grows on the interface between water and diesel, so I suspect that you have a small amount of water in your tank. The filter is doing what it should, separating water out of the fuel, and the bug is also, on the face of it, growing in the separated water.

You need to get access to your tank, either through a hatch or through the tank level sensor, and see what is in there. I used a Pela pump to remove the small amount of water in my tank that was allowing bacteria to multiply. Clean out the tank as best you can, and use a pump like the Pela 6000 Oil Separator (right) to remove water and free bug residue. Then use a product such as Marine 16 to treat the tank: they also make a continuous treatment, which I use as a preventative.