Sps:- tip burn,

[Uno Reef]

Burnt SPS tips often relates to nutrients, especially nitrate, too low, when alkalinity is higher than about 7 dKH or so.

So if the Nitrate too low how im seting best alkalinity, my sps always burn, my nitrate always 0....

 

[Randy Holmes-Farley]

So if the Nitrate too low how im seting best alkalinity, my sps always burn, my nitrate always 0....

Undetectable nitrate isn't good for other reasons as well. I'd recommend raising the nitrate by feeding more or dosing nitrate, rather than lowering the alk to reduce chances of burnt tips.

But if you want to go the alk route, aim for 7 dKH when nitrate is very low.