50 gallon on a shelf

I am plumbing a 50 gallon tank to use as a fresh water supply tank (for top off and salt mixing). I have it mounted about 6 ft in between two walls (4 ft apart). I used 2x4 screwed to the studs on both sides and back and rested a sheet of 3/4" hardwood on top, foam and then tank. This seemed reasonable and now i am having second thoughts. any opinions?

 

I build all my stands from 2x4's as long as the 2x4's are used so the 1.5 in is the crown. and if you have second thought then double then up and but where each one is screwed to the vertical studs put a chock like block scabbed on to the vertical stud right up under the king 2x4's you now have .. a chink of 2x4 8 in long and let what you have now to just transfer the load stresses .

 

Hum, that is a good idea. Ill post a couple of pics.