Looks good. Just a word of advice because I am a carpenter for 21 years and have seen alot of people building stands. Prior to 2003, wolmanized (better known as pressure treated) lumber was impregnated with CCA (Chromated Copper Arsenate). It was eventually banned because of the arsenic that was used to produce it.
Today 95% of the wolmanized timber sold in the US is now known as ACQ (which contains Alkaline, Copper and Quaternary Ammonium compounds). Although much better then the previous CCA, it also has its drawbacks. The worst is this material was released without educating the public on how to handle and work with it. I'm not going to go into the whole shmeel about wearing a mask, gloves, etc... but the #1 thing I see the beginner or novice do, is the use of improper fasteners. The chemicals in this lumber are highly corrosive to steel in general including steel fasteners, EVEN hot dipped galvanized fasteners. I've seen first hand, decks fail and fall apart because of this. Dont get me wrong its a great material but be sure to use the proper fasteners unless one day you want to come home to it laying on the ground or hear a sudden boom in the middle of the night. Even the brackets and hangers you see in Home Depot or Lowes are not the right ones to use. These big box store carry
Simpson Strong Tie hangers and brackets. If you dont see on the hanger or bracket the words ''Z-max'' or ''ACQ Certified''this is the improper hanger, bracket or fastener to use. I have seen a standard joist hanger used on an exterior wooden deck fail in under a year.
Anyways, to make it short, be sure any fasteners you use with this material are either stainless, ceramic coated or atleast DOUBLE dipped galvanized and the brackets or hangers say Z-max on them.
I'd hate to hear someones 2-300 gallon tank came crashing to the ground.
Here is a pic of an 8 month old deck. The homeowner built the deck himself using ACQ pressure treated lumber along with hot dipped galvanized nails and standard joist hangers.