More advice I would give you is to not overdo it with screws. When you're screwing into the end grain of a board, if you use too many screws, you run the risk of having that board start to delaminate at the end grain as the screws are pushing the layers apart. I see some tanks with screws every 2" and IMO that is a huge mistake. Also, as stated above, the glue is the main strength of the joint, the screws help a bit, but are more of a temporary hold while the glue is drying.