surferjo the diagonal brace in the picture are the suggested backframe for those who want to add a 3rd tier, which i do not want to do. so i will not be adding to my build. the drawn in shelve in the middle i just want to use for (2) 2.5 gallon tanks i have which should hold with no problem using 2x4's. the bottom area where the other tank is i think i will use for storing tank supplies or have the 10gallon as either an overflow tank or quarantine tank, i havent decided yet.
im a novice builder and i just had to google what a carriage bolt was. well ive seen them around but honestly i dont know how to screw them in all the way, i figure u use a wrench for the most part but dont know how u get the last part to go in all the way, i was just planning on using some long screws and going in at an diagonal angle from the leg to the top.
as luck, fate or badluck depending on how u want to look at it, i was able to finish putting together the top and bottom then ran out of screws, so i wasnt able to put on the legs to either, which will allow me some to think on how to screw those suckers in.
other words of note: watching documentaries on netflix while putting together a stand will slow u down considerably :P even saw one on piano making and in it a guy says this isnt screwing 2 by 4 togethers and i thought "hey thats what im doing!!" here's where i stopped earlier tonight. btw thats a nice and simple design u have there surfer, i like it, had i seen it sooner my probably wouldve used that instead.