Hopefully got the leak on my fluval 405 sorted.
First i siliconed the inside of the canister. only one corner was leaking but I thought I might as well do all 4 while i was at it. To be honest this probably would have been enough to stop the leak.
Next I filled up my lunch box with a load of silicone, it was the only thing I could find big enough to fit on the bottom of the canister, then sat the canister in it.
then left a few books on it over night untill the silicone had set.
Probably a bit over the top but I wanted to be safe than sorry and silicone is cheap. fingers crossed it will work ok.
Just got to find a new lunch box for work tomorrow!