Raising Alkalinity in Filtered Sea Water

[cmcimino]

I use filtered sea water for all water changes on my 28 gallon nanocube. The filtered sea water is always at 7dKH, 420 ppm Ca, and 1280 Mg. I've been advised to bring up my alkalinity to 8.5 to 9 in order to keep LPS corals. Can I just raise my alkalinity by dosing enough sodium bicarbonate to raise the new filtered sea water to 9 dKH? I don't think I will need to dose any Ca because I do 25% water changes weekly. Once I get more corals and have a higher nutrient uptake I may need to. Would I benefit from raising the Mg levels to 1300-1320?

 

[CodyRVA]

There are benefits to raising your ALK to 8-9 for more than just LPS. If you're not carbon dosing then sure raise it, if you are carbon dosing, then I would keep your ALK between 7-8. So, if you do want to raise your ALK, then yes I would dose, but make sure you're doing so consistently. As most of the experienced reefers will tell you; it's better to be consistent than to chase a magic number. If your tank comes in at 7 dkh daily, thats much better than 1 dkh shifts, daily, between 8 and 9. Same goes for MG, dose if you want to raise it, I would keep it at least at around 1300, ideally 1350s (just my preference), but same emphasis on consistency and stability over number chasing.

 

[Randy Holmes-Farley Verified Community Expert]

I'm not sure I'd boost the new salt water as opposed to just boosting the tank as needed, but you can easily boost either one using baking soda.

You'll not notice any difference between 1280 ppm and 1300 or 1320 ppm magnesium.