How mag to add to my tank

[Alvin88m]

I have a 75g Tank. I tested my water and my mag level is at 900. Which I was told is really low. Does anyone know how much mag I should add to my tank?

[downbeach]

What are you using to test it with? What salt mix? What's your SG?

[Alvin88m]

Honestly I took a water sample to the LFS but they didn't tell me how much dose it with. And I buy a salt water pre mixed I should ask what they use huh?

[downbeach]

Honestly I took a water sample to the LFS but they didn't tell me how much dose it with. And I buy a salt water pre mixed I should ask what they use huh?

If they are mixing at a low SG, then your Ca, Alk and Mg will also be low. What is the size of your system? Is it fish only?

[Rbs07fxstc]

Do you have corals or fish only or new setup? How long has tank been setup? Regular water changes should keep your parameters stable for a basic tank. If its a fish only tank then a low mag won't hurt. But it's a good practice for reefing to keep it stable. Most stores keep SG lower than what we keep our tanks at. So that keeps cal & mag low also.

[Alvin88m]

If they are mixing at a low SG, then your Ca, Alk and Mg will also be low. What is the size of your system? Is it fish only?

The cal, and alk were good the only thing that was low was the mag. I have corals and fish.

[Alvin88m]

If they are mixing at a low SG, then your Ca, Alk and Mg will also be low. What is the size of your system? Is it fish only?

It's a 75g

[downbeach]

What are your Ca, Mg and Alk reading? What are you using for test kits? I'd be surprised if your Ca and Alk were OK, with your Mg that low.
What are you using to top off with(evaporation)?
If I were you, I'd invest in a decent RO/DI unit, salt mix and start making your own SW. Get a decent refractometer (http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=9957), along with some calibration solution (http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=18717&rel=1), and mix to a SG of 1.026. You'll find it much more cost effective, and you have control. Your LFS is likely mixing it low, which would be OK for fish, but your coral should be higher. The other issue with buying from a LFS, is you don't know the quality of the water, i.e. it may be only RO, which may leave some unwanted nutrients in the water you're buying.

[Alvin88m]

Do you have corals or fish only or new setup? How long has tank been setup? Regular water changes should keep your parameters stable for a basic tank. If its a fish only tank then a low mag won't hurt. But it's a good practice for reefing to keep it stable. Most stores keep SG lower than what we keep our tanks at. So that keeps cal & mag low also.

I have corals. It's been set up a little over two months. My cal is fine my mag is the only thing that's low. So if I do a water change it should go up?

[Alvin88m]

What are your Ca, Mg and Alk reading? What are you using for test kits? I'd be surprised if your Ca and Alk were OK, with your Mg that low.
What are you using to top off with(evaporation)?
If I were you, I'd invest in a decent RO/DI unit, salt mix and start making your own SW. Get a decent refractometer (http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=9957), along with some calibration solution (http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=18717&rel=1), and mix to a SG of 1.026. You'll find it much more cost effective, and you have control. Your LFS is likely mixing it low, which would be OK for fish, but your coral should be higher. The other issue with buying from a LFS, is you don't know the quality of the water, i.e. it may be only RO, which may leave some unwanted nutrients in the water you're buying.
Idk what the LFS use to test it. My Ca is at 440, Mg is at 900 and my alk is at 9 degrees? My SG IS AT 1.023 idk if that affects anything

[downbeach]

Idk what the LFS use to test it. My Ca is at 440, Mg is at 900 and my alk is at 9 degrees? My SG IS AT 1.023 idk if that affects anything

I would add a few test kits to what I've already suggested, one each for Ca, Mg and Alk. Salifert would be a good one, or the new Red Sea Pro has a kit that contains all three.
If you aren't in a local club, I'd look for one, and try to enlist some help locally, I'm a little suspicious of your LFS.

[Alvin88m]

I would add a few test kits to what I've already suggested, one each for Ca, Mg and Alk. Salifert would be a good one, or the new Red Sea Pro has a kit that contains all three.
If you aren't in a local club, I'd look for one, and try to enlist some help locally, I'm a little suspicious of your LFS.

Thanks for your help. Usually I deal with owner and he's great I never have a problem with him but this last time I went this two kids that really didn't look like they knew what they were doing tested my water I guess I'll go back when the owner is around and I'll def buy the test kits so I know for sure what going on. Thanks for the help again

[Rbs07fxstc]

I have corals. It's been set up a little over two months. My cal is fine my mag is the only thing that's low. So if I do a water change it should go up?

It's odd for your mag to be low but everything else is good. Since your tank has only been up 2 months then I'm guessing you just have softy corals. Like zoas, shrooms & such. Usually your cal will be low if your mag is low. It's really hard to dose & keep good cal with low mag. So I bet the lfs messed up the mag test. But as you get into lps corals then u should test cal, alk (dkh), mag. But yea regular water changes can keep your parameters stable & corals healthy. Unless you got a fairly stocked coral selection, then u gotta start dosing.

[Alvin88m]

It's odd for your mag to be low but everything else is good. Since your tank has only been up 2 months then I'm guessing you just have softy corals. Like zoas, shrooms & such. Usually your cal will be low if your mag is low. It's really hard to dose & keep good cal with low mag. So I bet the lfs messed up the mag test. But as you get into lps corals then u should test cal, alk (dkh), mag. But yea regular water changes can keep your parameters stable & corals healthy. Unless you got a fairly stocked coral selection, then u gotta start dosing.

I have a acan lord, a neon trumpet coral, and a pink hammer. Also a montipora that came on a live rock I bought. I went back earlier today and got it tested again by the owner and the mag went up to 1020 and so did the Ca to 460 and the alk went up as well to 10 degrees. I'll be doing a water change tomorrow to try and get it back to normal

[Rbs07fxstc]

If the salt water you are buying is a low grade salt then it's not really gonna help much with a water change. You either need to to get a decent brand of salt water like Red Sea salt water or your gonna have to start dosing to keep parameters up. I would just buy my own salt & start mixing at home. Your SG is low at 1.023 when it should be 1.026, you can still buy your Ro/Di water from store if you don't have a system yet. Just buy salt to mix at home. If you can swing the extra few bucks then get a refractometer & 1.026 calibration fluid. You can get them cheap from online vendors.

[Alvin88m]

If the salt water you are buying is a low grade salt then it's not really gonna help much with a water change. You either need to to get a decent brand of salt water like Red Sea salt water or your gonna have to start dosing to keep parameters up. I would just buy my own salt & start mixing at home. Your SG is low at 1.023 when it should be 1.026, you can still buy your Ro/Di water from store if you don't have a system yet. Just buy salt to mix at home. If you can swing the extra few bucks then get a refractometer & 1.026 calibration fluid. You can get them cheap from online vendors.

Wht a a good brand for a refractometer?

[Rbs07fxstc]

I'm sure it won't be hard to find a good brand but I just use a cheap refractometer. I think I might of paid maybe $30. Just keep it calibrated with 1.026 solution. Bulk reef supply & marine depot sells them pretty cheap online.

[downbeach]

See the hyperlinks in post #8

If you buy both you'll get free shipping.