You are wanting to put that tank on wheels? Do you know what the weight capacity of those casters is? Do any of the casters swivel (otherwise you will only be able to go one direction)?
You are wanting to put a 950 gallon tank on wheels, which is going to end up being nearly 10,000lbs. Just to put that into perspective, that is near the same weight as two Suburbans. I really think you should think long and hard about putting wheels on the bottom of this tank.
I'm going to give you some perspective on casters. I own a piano moving business and we use 5" casters on our dollies. Each caster is rated for 250lbs. I've had numerous casters spit bearings, shackles fold, wheels split, etc while moving concert size pianos (1000lbs+). I would suggest buying something heavier duty than the pictured set you have.
The point of the casters is that there is a wall with a pair electrical outlets behind the tank and a window. If for whatever reason I need to get behind the tank, I can lower the water level in the tank, wheel it forward, and get behind it. The tank is actually only holding 800 gallons of water.