Adding supplements

i do water changes every Wednesday and Thursday to my tanks. My question is should i be adding supplements right before a water change? Or should i be adding them to the water change water that i am mixing? Just seems that if you add expensive supplements a day before a water change than half of it is going down the drain?

 

I would add them to the water you're putting into the tank.

 

cool. well i am using Tropic Marine Pro Reef Salt. I usually mix it to a SG or salinity of 1.024, which allows me to keep a 1.026 level in my tanks with top offs.
I just tested the Mag, Alk, and PH levels of the water change water that is mixing up......
SG 1.024
PH 8.1
Alk 4dkh
Mag below 1225
Also how long should i wait after a water change to test my levels?

 

How would i know how much supplement to add to the water change water to get a certain level in my tank after the water change?

 

Measure your parameters before you do the water change to get your current Calcium, Magnesium, and Alkalinity levels.

System volume: Use how much water you are replacing with your water change, not how much water is in your total system.

3reef.com - Forums for coral reef aquariums, salt water fish, corals, inverts, protein skimmers, aquarium lighting and more - Calculators

Go to the additives section and use the calculator to figure out how much of each you will need to add to bring your parameters back up to where they were before you did your water change.

 

which calculator do i use? i dont get it ;(

 

Below where it says "3reef Aquarium Calculators" click on the one that says additives. It will be self-explanatory at that point.

 

The suppliments will tell you in their instructions how much to add to raise X amount.

 

what supplements are we even talking about here?

 

ok got it. i have 5gallons of water change water with a PH of 8.1, Mag of 1225, and Alk of 4dkh. So i would add .5tsps of SeaChem Reef Buffer for Alk to bring it up from 4 to 10 and to bring PH to 8.3. Than to bring Mag up from 1225 to 1400 i would use 8 1/3 tsps of SeaChem Advantage Magnesium.
I am only using about 2.5gal for my 14gal and the rest for my other tank.
So im thinking that this water change will bring my 14gal up to 10dkh from 9dkh this morning and will definately raise my Mag up a bit from 1312.5
How does this sound guys?