I would just try patch up the holes in the tank and start over.
As far as the UV unit you have, do you have a MFG and part number? It may be easy to look it up and see what it is , and determine what you can do with it.
I really should start hacking and whacking out a simple RAS for PB members. The new galvanized stock tank has been outside, full of water since early spring. It is under a canopy and no algae, or even skeeters took a shine to it. Reason for doing that is I am leaching out the Zinc, and corroding it a bit. Makes it a bit easier to scuff up and coat with epoxy. I know it is toxic, as my dog wont come near the water in the tank. I had a 30 gallon polypropylene barrel collecting water off the canopy not much more than 3 feet away, still out of direct sunlight. And it was full of Algae and all stages of skeeter development
Not a perplexing issue to me, as I know what is taking place. But you can get some really "clean" flow characteristics, and suck out and contain the TSS (Total Suspended Solids), before they turn into TDS (Total Dissolved Solids).
I suppose, that is another chapter!
