This is a custom prefilter that I am making for my 18 gallon tank. Going to go to TAP plastics and have them make it for me this weekend. Thought I would share the drawings in case someone else was looking for something similar.
If I am correct, this is for an in the tank application and will have a tube inside the prefilter that siphons into the main filter. The reason this is such a good idea is it skims off the surface water which contains the majority of impurities in the water. It is also a good idea for an intake for a canister filter since it wont allow the tank to completely drain in case of a seal or something going out on the cannister. Nice work and thanks for the info on the hood as well.
now my thinking is that if you curve corner the front panel...that you would need slightly longer front panel right? say if you wanted it 2 x 4 x 2..... then you might need it a lil longer than 8 inches? is that correct or 8 is fine?
also, how do you mark and know exactly where to make the bend to be accurate enough so that the edges of the front panel are flush after you are done...