zach c.;954920; said:
What sketch program are you guys using? Great diagrams which I cant reproduce so this makes my explanations harder.
Provided you have the side support braces on front and back panels (to prevent side panels flexing) it doesnt matter how close to the end these braces stop. Even 15cm away from the end panel is okay since the flex is minimal that close to the end. So where you want to stop the side support brace and how you finish the glue is purely cosmetic. Have a look at some actual tanks if your unsure.
If this a turtle tank and you wont have any lids then you dont need any side braces on the end panels. You will need some cross braces still. I am lazy so I dont preglue any support braces on the end panels, I run my side support brace quite close to the end panel and treat the actual end support as another cross brace. The side support brace on a tank your size is just to stop fish jumping out and something to support lids.
Zach,
Some build steps as per your PM:
1) Pre-glue support braces for front and back. I would use 50mm x 6mm glass for side braces since your tank is long. This is good practice for applying your glue in long straight runs of even thickness (beads). Aim for a single round bead of glue about the width of your glass (6mm) a few mm in from the edge. This is also the best place to make mistakes safely and you can wipe clean with a methalated spirit soaked rag or just scrape clean and start again. Allow these to dry - On a warm day, 6 hours is enough but your unsure then 24 hours is safe and plenty.
2) lay out all glass panels as per your diagram 2 above to help you get organised and reduce moving glass later. Make sure all glue areas are clean and dry. Only apply glue to one panel at a time. An extra person is recommended on a long tank if this is your first... 2 extra people if your really nervous

Alternatively a house brick with one corner missing can be used - the missing corner allows a gap for glue line
3) Glue one of the end panels first and then stand it up gently press into place.
4) Get your helper to hold this in place while you glue the other end panel and repeat.
5) Glue your first side panel. This involves running the glue down 3 sides but there is no need to rush. When ready, gently stand the panel up and align the 2 end panels to be vertical and in line with your first side panel before pressing into place. Dont press too hard but enough your silicon is pushed out. About 1mm away is okay. This is the time to check for air bubbles. Wont be any if your glue bead is straight and uniform. Hold this side panel in place with some masking tape. You could have some tape pre-cut and ready if your alone.
6) Repeat for the other side panel. This will be much easier since the end panels are already in place and parrallel. You could smooth inside glue now with a wet finger or curved plastic (like ice cream container lid) or just leave it. If there are no air bubbles, it will hold water.
7) Since the side support braces are already firmly dried, I usually add my cross braces now. Just add some silicon glue and place cross braces on top of the side braces. I let gravity hold in place but you can clamp if you wish. Do try to space cross panels evenly or you will need to cut custom lids. On some tanks, I allow a small gap in the corner for heater/filter cords, on some tanks with escape prone fish, I dont. As I mentioned before, this part is just cosmetic so whatever you want. Lids and handles are also up to you. I prefer a back sliding lid approx 40:60 but these need a special plastic trim for the slide.
Dry time is 24 hours before move and 3-4 days before fill. Its just a small tank (only 6mm glass) so it will dry fast. Use construction grade silicon if you can but this is much more sluggish and harder to work with.
Go over the process several times in your mind and let me know if you have further questions.