You pick the change poll

[Delphinus]

Not sure about either one to be honest.

Thoughts on Mg: IME, Mg technically isn't a problem unless it's very low. I do actively dose Mg I suppose you could call it, but I do it via my water changes: I add just enough MgCl and MgSO4 to my new water to bring it up to around 1500. That tends to keep the Mg in the tank at "good enough" levels. So I don't think "worry" about Mg. It's just a routine.

I don't understand the science behind it, but I've noticed that things just look better when Mg is at "good enough" levels (versus "far too low"). The change is most noticeable in anemones (of which I have a handful). Ever since adopting the water change technique however I haven't noticed them looking off due to Mg levels in probably 4-5 years now or more.

Guess the thing to try is seeing if your Mg is low, then dosing it back to seawater type levels, then see if you notice a difference in your tank.

Thoughts on carbon: I used to think that reactors were a better choice for carbon as I thought water passing through the column of carbon would make for better absorption of the baddies because of better contact to more surface area blah blah blah something or other. But seem to have read more than a few credible articles in the last few years that seem to suggest just having a bag in a high flow area in the sump is good enough because osmosis or something blah blah blah the main take away is it still works as carbon.

I made the investment in TLF reactors so I figure I might as well use them for carbon but if I didn't have them already I'm not sure I'd worry about it too much.

Guess the thing to try is move your carbon into a reactor and see if you notice a difference in your tank.