Cat 257B 05 Model Fuel tank rust

[Daddygoose51]

I need help figuring out what to do about the rust in my fuel tank. The tank is built into the machine so no way to take it off to clean. I tried the Apple cider vinegar trick but still have rust . the 257b has two fuel filters which i have to change the smaller one about once a month due to the rust sediment. is there something on the market to treat the tank that doesn't cost an arm an a leg?

 

[Tazza]

I have heard of a product called evaporust, but to fill a fult tank will be stupidly expensive.
I wonder if you use a different type or filter that is larger as a primary if it will help not plug up so fast.