bulkhead

I'm building a new DIY RDWC build. Should it be: (a) just like the picture in the attachment... (b) kind of like the attachment, but 2 bulkheads on each bucket (c) more like a "Current Culture" kind of setup with an undercurrent... (d) try this...

Doesn't say anything on the bottle regarding aquarium use. I've noticed my bulkheads leaking on the inner side (where the pipe is inserted) as well as from the outer rim of the bulkhead so I've turned to silicon sealant. What do you guys think? Anyone have experience using this in hydro...