Awesome dude, I am so envious. (I'll use my foul language when I see you)
Couple of questions and remarks
1. I dont think you should of sank the whole sump in so low, going to be fairly easy for stones or rubbish to end up in there. Is it not possible to lift is say 300mm above the floor level? It should still be low enough for the rest of your tank
2. I see no draining holes, where would all the water go to? I'm sure you thought of this, just checking with you.
3. Are you still going with glass? I would like to see how you going to join the glass or film to that steel frame, if you dont mind I'd like to see many pic of that process. (it's easier to steal other people's ideas than to waste time in trying to figure it out

)