DYI Stand Plan, how is this idea?
 

I have a 75 Gal tank that I am building a stand for. I attached a quick picture that I did in paint, because for the life of me I can't figure out how to use sketchup.

What I was planning to do is build the stand deeper (front to back) than my tank is. I was going to sheet the top in plywood and then drill 1" holes and run my plumbing down into the sup below. This way I can have the stand tight against the back wall and most of the plumbing is hidden within the stand.

From the picture below:

- All joints will be secure with pocket holes and screws.
- The tank will set on the portion between the bottom black line and the blue line.
- The small section at the top of the picture will be behind the tank and I want to run the plumbing down through there.
- The bottom frame will be the same at the top frame.
- The frames will have lot of support via 2x4 uprights.
- The upper frame will be made of 2x6, the bottom will be 2x4
- Uprights will be 2x4

Is this all fine?

Looks good to me. I would use 2x6 joist hangers at the ends of the blue line, and glue and screw everything with PL Premium just for some overkill.

cool, thanks

stand
 

if you are going to have doors below you might want to double up the front joist.also i have been building a lot of stands and you don't really need 2x6.2x4 on edge is fine.carry all your jack joists with studs to support the top.get rid of the blue joist and just drill your holes through the plywood.all your green jacks will carry the weight

What's the need for the double joist at the front?

Monocus is correct. With a 75 gal, 48" tank, 2X4 is fine. But being a contractor and seeing literally 100's of studs a week, I certainly would want to personally chose those that I would use. I can't believe the crap their allowed to sell.
I would also lose the Blue joist as it's really not necessary and just complicates the design.
Just make sure when you're laying out the joist spacing that one isn't where your holes in the tank are. And keep the joist to no more than 16" centre's.
I personally don't like using pocket screw for anything structural. If the stand is being skinned or covered in any manner, those screws will be hidden anyway. In any floor joist application, if you can end nail ( through the rim joist at 90 degrees into the end of the joist) you don't need hangars.
As far as doubling up the front rim joist, it potentially has it's merits. In the back, you're more than likely going to skin it or even put a stud midspan to help carry the weight. But in the front, if you have a sump, you may not really want anything preventing you from slipping a sump in there or at the very least have a support that's removable so you can do so. The limit there though is (if that's why your putting it in there) you really shouldn't remove it while the tank above is full. It's only on set up, before the display is filled, that it can theoretically be safely removed.
In this case, a stand builder may decide for extra insurance, and to help strengthen that front support, instead of putting a stud mid-span, to double it up.

stand
 

in the back i put studs every 16 inches,but i dado them out so they are removable and can be easily be replaced.the double joist in the front helps carry more weight if you are putting doors on the front of your stand

Sweet, makes sense. Thanks for the help.

Spend lots of time picking your wood. Look for cupping, warping, twisting. If you have a table saw, run it through one side, then shorten the fence and run the other side for more square edges. 2x4s tend to have rounded edges. Check out the beginning of my build thread to see what I did.
Good luck!