Is my tank doomed?

I asked my neighbor to feed my beta while I was gone for a few days. I literally told him just feed him a small pinch of 4-5 pellets twice a day and I return to this mess with pellets EVERYWHERE in the tank. I have no idea why he did this or what happened, I should've just invested in an automatic feeder. Will this much excess nutrients kill the tank and my fish? Is there any way to save my tank if thats the case? I'm not sure how to approach this