To Dose or Not To Dose?

[rdnelson99]

Yesterday I had my water tested at a LFS. For the most part it matched my test from that morning however I do not have a test for Magnesium. My tank is a 45 with 40 lbs LS, 20 lbs LR, 10 lbs base rock up and running now for 5 weeks. 9 days ago I added 2 clowns and a small clean up crew. Yesterday (after this test) I added a 6 Line Wrassle, a Fire Shrimp, a few more snails and two small coral frags (my first fags). So far I have used filterred tap water (making my first batch of RO/DI right now)

Here are the results of the LFS test.

Am 0
Nitrite 0
Nitrate 0 (mine was 10)
PH 8.3
Alkalinity 9 (my reading was 143.2 kh or 8)
Calcium 440
Magnesium 875
Phosphate 0
Salinity 1.025

The guy at the LFS IMMEDIATELY tried to sell me a PH buffer and a supplement for low Magnesium. From all I have heard here, I should shy away from supplements unless needed. My question, is it needed? According to this LFS magnesium should be between 1250-1350. Is that correct?

 

[ccCapt]

Yes, your mag test is definitely showing it being low but.....I would question the accuracy of that test. Being your tank is only 5 weeks old there is no way the mag should be that low. What salt do you use? All of the major synthetic sea salt mixes have mag levels considerably higher than what that test shows.

There is absolutely no need for any buffers as your alk is fine and any alk buffer you use will also affect your pH, which is also fine.

This is a great guide for where you want to keep your water parameters.
Reef Aquarium Water Parameters by Randy Holmes-Farley - Reefkeeping.com

 

[rdnelson99]

I am using Instant Ocean salt and mix it myself. Your answer makes a lot of sense to me and I trust it much more than this LFS. I only went there because I wanted my wife to see the displays they have (gorgeous). But, they have given me bad advice in the past and they are extreamly expensive. My plan was to let her see what things look like in an established tank to help her choose better at the LFS I do trust (he has a bare bones store but is a great guy and gives good advice).

I use LPI Saltwater Master and Reef Master kits. Neither has anything that test Magnesium. Is there one I can get sepparately or should I even worry about testing for it?

 

[ccCapt]

I use Salifert test kits for calcium, alk and mag (that's all I test for). They are a bit more expensive than other brands, but they are extremely accurate and easy to read the results.

Your calcium and alk reading are close to what you can expect from Instant Ocean. You should see mag around 1350.