I don't think it is doomed... BUT I used to use Tap Water and it is terrible , I had all kinds of algaes!!!
so... try to get some containers and try to start buying R/O water... maybe a walmart location. Have you checked phosphates??
Those were killing me as well.... In other words... is going to take a lil to bring the nitrates and phosphates down... but it can be done... lots of water changes.... try to get a phosban reactor... or simple put some phosban in a filter bag and dump it in the sump... (worst case escenario).

My tank was perfect for 3 months and then... BOOM, algea all over the place....

So BUY water from LFS or Walmart.... 25 cents p/gal until you get your unit.

Ohh and very good thing that you have lots of hermits, snails and nubiranchs 8)