Glory Be To Godzilla

Is there any safe way to reduce nitrates without doing a massive water change? My tank (75 USGal) chemistry has been out of whack for a while and I've managed to bring the pH closer to safer levels, ammonia is close to zero, and there’s no nitrates. However, my nitrates are at 80ppm and it’s extremely worrying. I know it sounds like I’m being neglectful but I’m trying very hard to make sure things can get better.

I have done the following:

- Add living plants to water

- Stopped using slow-degrading food

- Cleaned the filter (Big filter rated for 150~ USGal, with ammonia rocks and big charcoal baggies)

And I haven’t introduced any fish since the die-off a couple months ago thanks to me being an absolute fuckhead. I’m very worried that my fish are suffering and I want them to be healthy again.

Also, if a big water change should be done, I have no issue with that, it’s more an issue of time (thanks to work) more than anything. To add to that, please recommend me safe water to add to the tank to avoid shocking my fish with dangerous pH changes.