yikes heavy nitrates reeked havic in my reef

[Delphinus]

Short of doing a 100% water change you actually can't do water changes to zero - but you can make a significant reduction before you hit the point of diminishing returns.

4 - 10% water changes would leave you at 65% nitrates from before, whereas 1 - 40% water change (same water volume changed out) would leave you 60%. Not too much different.

But 10 - 10% water changes leaves you with 34% nitrates from before, whereas 1 - 100% water change (again same water volume) leaves you with zero.

Kind of hard to do a 100% water change though Possible (I've done it), but extremely difficult given the water volume required and if you have fish that will be affected.

Nitrates don't have to be zero. If you can get them to <10 you're pretty much set, let the tank handle the rest. Less is better but that can be handled with careful nutrient management (ie. skimming, watching how much you feed, pruning macro algae, etc.).

What are the current nitrate readings?