He does have a RO/DI, not sure on what salt brand though. I think Reef Crystals?
First off, I agree that water changes should be the first move before dosing anything! Also, if/when you dose, read the instructions carefully, and keep a calculator handy. Don't forget to estimate how many gallons are being displaced by your rock too... you probably have 10-15 gallons displaced by your rock. You should include the volume in your sump too of course.
I've used the Brightwell Magnesion but not the Elemental. It's a pretty good product but there are much cheaper alternatives that you can get. Bulk Reef Supply sells it where you mix the main ingredients with your RO/DI and you get a gallon for around $10. The Brightwell product is pre-mixed, but you get 17 oz. for about $8. Big difference in cost! I believe the BRS product is more Mag sulfate in their mixture than most commercial brands too.
The Magnesion will get your Mg up to where it should be. This is strictly a concentrated magnesium supplement. Don't add more than the recommended daily dosage! Slower changes are better for just about everything in this hobby.
The Elemental looks like a combo of Cal/Mag/Stront. This is probably good to add maybe once a week to try to keep your params balanced. Probably not as good as a 2-part system, but essentially it's trying to do the same thing if you also dose an Alk supplement. I'd be cautious with this one because, although Strontium is an essential element in reef tanks, you don't have a test kit for that and I'm not sure the +/- of having too much of that.
I'll say it again though Dave... I think your tank is too young to really need to be supplementing anything. You should do a full run of tests on a fresh batch of salt before you add it to your tank (maybe an hour or two after mixing it) and see what you get for Ca/Mg/Alk. It might just be your brand of salt or maybe a bad batch that's giving inadequate levels of these. If that's the case, then a million water changes won't fix the issue (but dosing could correct it.)
First off, I agree that water changes should be the first move before dosing anything! Also, if/when you dose, read the instructions carefully, and keep a calculator handy. Don't forget to estimate how many gallons are being displaced by your rock too... you probably have 10-15 gallons displaced by your rock. You should include the volume in your sump too of course.
I've used the Brightwell Magnesion but not the Elemental. It's a pretty good product but there are much cheaper alternatives that you can get. Bulk Reef Supply sells it where you mix the main ingredients with your RO/DI and you get a gallon for around $10. The Brightwell product is pre-mixed, but you get 17 oz. for about $8. Big difference in cost! I believe the BRS product is more Mag sulfate in their mixture than most commercial brands too.
The Magnesion will get your Mg up to where it should be. This is strictly a concentrated magnesium supplement. Don't add more than the recommended daily dosage! Slower changes are better for just about everything in this hobby.
The Elemental looks like a combo of Cal/Mag/Stront. This is probably good to add maybe once a week to try to keep your params balanced. Probably not as good as a 2-part system, but essentially it's trying to do the same thing if you also dose an Alk supplement. I'd be cautious with this one because, although Strontium is an essential element in reef tanks, you don't have a test kit for that and I'm not sure the +/- of having too much of that.
I'll say it again though Dave... I think your tank is too young to really need to be supplementing anything. You should do a full run of tests on a fresh batch of salt before you add it to your tank (maybe an hour or two after mixing it) and see what you get for Ca/Mg/Alk. It might just be your brand of salt or maybe a bad batch that's giving inadequate levels of these. If that's the case, then a million water changes won't fix the issue (but dosing could correct it.)