Fish tank - have a 16mm rubber pipe leaving the tank with a pump on one end in the tank.

Out doors - drain.

How do i get through the wall to the drain?

option 1 is drill through and run the rubber pipe through the wall - polyfilla around the pipe. Just stick pipe into a standard waste pipe and run it the 0ft to the drain.

Option 2 is to bring the waste pipe into the house and have some way of joinging the two.

Option 1 is easy

option 2 means i could unhook the pipe.

Both look a bit messy - is there a wall plate i could fit over the hole to tidy the install up a bit?

Id be tempted to just drill through the wall and put a piece of solvent weld overflow style pipe through and push your pipe in or through it.. if you put it 'into' the drain then you need a trap really..

As for drilling through the wall, the only plate I can 'think' off are the style the sky installers use but I dont know where you would get one from, how about the things that go around radiator pipes ?

David